MOSCOW -- President Vladimir Putin of Russia on Sunday called on Ukraine to begin talks on "the statehood" of that country's rebellious southeast, a vague and provocative turn of phrase used by Putin as he demanded that the Ukrainian government negotiate directly with pro-Russia separatists.

Hours later, Ukraine said a border guard vessel operating in the Azov Sea was attacked by land-based forces.

Western governments have accused Russia of backing the separatists with arms and fighters and of sending Russian troops to lead a counteroffensive in Ukraine during the past week that threatened Mariupol, an important port city, and left thousands of government troops encircled.

"We must immediately begin substantive, meaningful negotiations, not on technical questions, but about the political organization of society and the statehood of Ukraine's southeast for the unconditional securing of the legal interests of the people who live there," Putin said.

Dmitry Peskov, Putin's spokesman, said that despite the use of the word "statehood," Putin was not calling for independence for eastern Ukraine. Rather, he said, the Russian leader was seeking inclusive negotiations that would provide greater autonomy for the country's southeast as it remained a part of the country.

The self-proclaimed independent republics in Luhansk and Donetsk, which held haphazard, self-organized referendums on independence in May, repeatedly have requested Russian recognition, protection and annexation. Although the Kremlin annexed Crimea in March, it has avoided for months formally recognizing the separatist states.

Putin spoke Sunday on a televised news program in Moscow as European leaders vowed at a summit meeting in Brussels to toughen economic sanctions against Russia by the end of the week if the conflict in Ukraine continued to escalate.

In the interview, Putin veered between veiled threats and demands for negotiations to resolve the conflict in Ukraine. He said that country should cease hostilities immediately and renew its supplies of natural gas, which are piped in from Russia, to survive the coming winter.

"I think that nobody thinks of that anymore, except Russia," Putin said of the winter. "There are ways of helping resolve the issue. First, to immediately stop hostilities and start restoring the necessary infrastructure. To start replenishing reserves, conducting the necessary repair operations and preparing for the cold season."

Putin, however, gave rare praise to President Petro Poroshenko of Ukraine after a meeting with him in Minsk, Belarus, calling Poroshenko "a partner with whom dialogue can be conducted."

Earlier, Putin toughened his rhetoric on Ukraine, making a direct address on the Kremlin's website to "the militias of Novorossiya," or New Russia, a controversial phrase for the region, including the rebel strongholds of Donetsk and Luhansk, which was once controlled by the Russian empire. In the address, he invoked the phrase to hail the success of the rebel offensive.

He called for the militias to allow for the opening of corridors for Ukrainian troops to retreat, a plea that was promptly granted by the prime minister of the self-declared Donetsk People's Republic, Alexander Zakharchenko. Zakharchenko said, however, that the Ukrainian forces must surrender their artillery and heavy vehicles.

First attack at sea

On Sunday, a spokesman for Ukraine's offensive against Russia-backed rebels said a border guard vessel has been fired on with artillery -- apparently the first incident at sea in the fighting.

The spokesman, Oleksiy Dmitrashkovsky, said the attack occurred Sunday afternoon but he had no further information, including how many people were aboard the boat.

The attack took place amid heightened concern that the rebels are trying to seize a land bridge between Russia and the Crimean Peninsula, which Russia annexed in March.

Until this week, the area along the Azov Sea had escaped the fighting that has gripped areas farther north since April.

Meanwhile, Col. Andriy Lysenko, a spokesman for the Ukrainian security council, said nine of the 10 Russian soldiers who had been seized last week had been given back to Russia in exchange for 63 Ukrainian servicemen.

Ukraine's Security Services said the Russian soldiers had been detained about 20 miles from the border and were evidence of the presence of Russian troops fighting in Ukraine. Russia claimed that the men had strayed into Ukrainian territory by accident during a routine border patrol.

"The negotiations were very difficult," said Alexei Ragozin, the deputy commander of Russia's Airborne Forces, according to the RIA Novosti state news agency. "However, common sense triumphed, and all ended well. The most important thing is that our guys are back with us, in Russia."

"I want to emphasize that we never abandon our own," he added.

On the eastern edge of Mariupol, a city of about half a million inhabitants on a bluff overlooking sunflower fields, workers from the city's Soviet-legacy steel plants and a few hundred volunteers were digging trenches and bunkers and filling sandbags to defend against the expected attack.

Men in hard hats and the gray and red overalls of the Azov Steel Works filled sandbags, stopping to wipe their brows in the midday sun. Asked why he was laying the steel slabs on the fortification, one man replied that he wanted to show Putin that he would not be welcome in Mariupol.

The workers arrived with flatbed trucks carrying steel slabs, yellow backhoes and mobile cranes to hoist over the tops of bunkers gigantic 22-foot-long and 7-foot-wide slabs of raw steel fresh from the blast furnaces. Each was 9 inches thick and weighed 25 tons.

"Everybody is trying to help in their own way," said Vasili Sisentsov, a steelworker.

Mariupol, considered a solidly pro-Ukrainian city, never fell under full control of pro-Russia groups. But the soldiers who seized the border town of Novoazovsk, 27 miles away, who claim to be from the Army of Novorossiya, say they also intend to capture Mariupol, but have not said when.

More sanctions

Elsewhere, the U.S. welcomed the EU's decision to prepare more sanctions against Russia and is working closely with the bloc and other partners to "hold Russia accountable for its illegal actions in Ukraine, including through additional economic sanctions," Caitlin Hayden, a spokesman for the White House National Security Council, said in a statement.

The administration called on Russia "to immediately" remove its military from Ukraine and end supporting the separatists, according to the statement. Russia denies that it's involved in the fighting in the neighboring country.

While EU leaders disagreed about possible military assistance to Ukraine, they gave the European Commission a week to deliver proposals for sanctions that may target Russia's energy and finance industries.

German Chancellor Angela Merkel said she opposes sending arms to Ukraine because it would be a signal that the conflict has a military solution. Almost 2,600 people have been killed so far, the United Nations said.

"The situation has very much escalated over the last two days, and if this continues we will decide on further sanctions within the week," Merkel told reporters in Brussels.

The EU and the U.S. have already slapped visa bans and asset freezes on Russian individuals and companies, and since July have imposed steadily tougher sanctions targeting the country's energy, finance and defense industries.

Poroshenko called for military and technical assistance for Ukraine from the EU. He said there will be a trilateral contact group meeting today with the Organization for Security and Cooperation in Europe, Ukrainian ex-President Leonid Kuchma and Russian ambassador Mikhail Zurabov.

Talks will focus on Ukrainian "hostages" held in Russia, the OSCE monitoring mission and a potential cease-fire, he said.

"I cross my fingers, I hope it will be a cease-fire," Poroshenko said, adding that he expects to publish a draft peace plan next week.

Information for this article was contributed by Andrew Roth, Andrew E. Kramer, Neil MacFarquhar of The New York Times; by Jim Heintz, Laura Mills and Peter Leonard of The Associated Press; and by Kateryna Choursina, Vladimir Kuznetsov and Ewa Krukowska, Jesse Hamilton, Stepan Kravchenko, Jonathan Stearns, James G. Neuger, Ian Wishart, Rebecca Christie, Patrick Donahue, Helene Fouquet, Bryan Bradley and Andrew Frye of Bloomberg News.

A Section on 09/01/2014