WARSAW, Poland -- Polish authorities said Friday that there are no more migrants camping along the Belarus side of the European Union's eastern border, but attempts at illegally crossing into the bloc's territory are continuing and becoming more aggressive.
And Ukraine, which also borders Belarus, said it would build a border fence and ditch and hold military drills to forestall any attempted influx of migrants.
About 50 migrants got through a fence into EU member Poland on Thursday, said Anna Michalska, a spokeswoman for Poland's Border Guard. They included a family of five who said they wanted to stay in Poland, opening a procedure toward settlement. The others will have to return to Belarus, Michalska said.
Two other large groups of migrants were prevented from entering. Some migrants have thrown stones and used tree branches to hit Polish border guards.
Hundreds of Iraqis flew back home from Belarus on Thursday after abandoning their hopes of reaching the EU.
Still, many migrants remained in a heated warehouse that Belarus recently made available near the border. They had been camping in a cold, wet forest since Nov. 8.
A charity collection was held in Michalowo, near Poland's border with Belarus, with local people and some from across the country bringing clothes, blankets, food, toys and other items for hundreds of migrants who have entered Poland.
Konrad Sikora, deputy mayor of Michalowo, told The Associated Press the reaction the charity is getting from all around Poland "is tremendous, it's great, and I think we are helping those people really, really deeply."
Some migrants, the most needy, are still in the damp woods, while others are in hospitals or in guarded centers for foreigners, waiting for their international protection applications to be processed. In most cases they are rejected.
NATO Secretary-General Jens Stoltenberg on Friday reiterated his warning that the situation on the border represents a security challenge.
"We are ready to provide support," Stoltenberg told reporters in Berlin.
He welcomed "the fact that Iraq is now taking back people and have stopped" flying migrants to Belarus.
He also noted that NATO has seen "a significant military buildup by Russia close to the borders of Ukraine [with an] unusual concentration of forces."
"We call on Russia to be transparent and to prevent an escalation and to help and to reduce the tensions along the borders with Ukraine," Stoltenberg said.
Meanwhile, Polish President Andrzej Duda, on a visit to North Macedonia, said that in recent talks with Stoltenberg he has "indicated all possible hypothetical military threats" that might emanate from Belarus.
"I believe that ... we are going to overcome this crisis and that the Belarusian regime is going to stop its hybrid attacks against our countries," Duda said.
Poland has notified Belarus it intends to halt railway freight traffic at the border crossing near Kuznica on Sunday out of security concerns because of the continuing presence of migrants at the warehouse there. Road traffic was stopped there last week.
Tensions flared at the Poland-Belarus border in recent days, with about 2,000 people trapped between forces from the two countries. On Tuesday, Polish forces at the border used water cannons and tear gas against stone-throwing migrants. Warsaw accused the regime of Belarusian President Alexander Lukashenko of giving smoke grenades and other weapons to those trying to cross the frontier.
The U.N. refugee agency says about half the migrants at the border area were women and children.
Information for this article was contributed by Daria Litvinova, Yuras Karmanau and Konstantin Testorides of The Associated Press.