"It involves taking the most stringent measures to protect the territorial integrity of our country," Lukashenko said.
Allegations by Belarusian President Alexander Lukashenko that foreign troops were operating near the country's border are baseless, NATO said.
Europe's longest-serving leader said on Saturday that NATO troops in Poland and Lithuania were "seriously stirring" near their borders with Belarus and ordered his troops into full combat readiness.
The 65-year-old leader ordered his defence minister to enact "the most stringent measures to protect the territorial integrity of our country."
NATO said the claims were "baseless".
"As we have already made clear, NATO poses no threat to Belarus or any other country and has no military buildup in the region," it said in a statement.
Both Lithuania and Poland have also denied the accusation.
"The regime is trying to divert attention from Belarus's internal problems at any cost with totally baseless statements about imaginary external threats," Lithuanian President Gitanas Nauseda told AFP.
Polish president's chief of staff Krzysztof Szczerski dismissed the claim that Poland planned to violate Belarusian territorial integrity as "regime propaganda", calling it "sad and surprising".
"Poland... has no such intention," he told the Polish news agency PAP.
Lukashenko made the comments while inspecting military units in Grodno, near Belarus's border with Poland, according to the president's press service.
His visit comes ahead of large-scale military exercises planned in the Grodno region between August 28 and 31.
More than 100,000 people flooded the streets calling for Lukashenko to resign last week.
Protests have swelled in Belarus since he claimed to have won 80 percent of the vote in the August 9 presidential ballot.
The opposition, who are seeking new elections and a peaceful transition of power, have called for another major protest on Sunday.
Demonstrators started taking to the streets of Minsk in the early afternoon.
“We had enough and want things to change. We are scared to be here, but we want to support everyone. We need to do this.” Victoria, 30, told Euronews in the Belarusian capital.
Another protester, Dima, 30, brought her child to the rally.
“Maybe we are crazy coming here with our kid, but we hope that it will give some protection for journalists and other people. We hope that it sends a signal to everyone that we are peaceful."
"Maybe, it is stupid, but this might be our last chance to protest if our leaders are arrested", she said.
Svetlana Tikhanovskaya, Lukashenko's election challenger, who is now in self-exile in Lithuania, said this week that Belarusians would "never accept the current leadership again" after the crackdown on demonstrations.
Lukashenko denied holding a fresh ballot, rejected calls to resign and said the opposition was attempting to seize power.
The EU has rejected his re-election and said it would impose sanctions against what it said was a substantial number of people responsible for rigging the vote and cracking down on protests.