Belarusian leader Alexander Lukashenko spoke at a rally of his supporters in Minsk on Sunday, stressing that no new election would be held and accusing NATO of massing on his country's western border.

Lukashenko also held a second weekend phone conversation with Russian President Vladimir Putin, who told the Belarusian leader that Moscow stood ready to provide help in accordance with a collective military pact if necessary, the Kremlin said in a statement.

Belarus is mired in nationwide opposition protests following the presidential elections on August 9.

The Belarusian president called on his supporters to defend the country. "I called you here not to defend me... but for the first time in a quarter-century, to defend your country and its independence."

"I'm not a fan of rallies, but alas, it's not my fault I had to call you to help me," the 65-year-old said as some 10,000 supporters waved national flags and shouted, "Thank you!" and "Belarus!"

He reiterated that the elections were valid.

He referred to the country's history and the successes of his rule.

"We built a sovereign independent country for the first time in our history," Lukashenko said, reminiscing about the "difficult years" of the 1990s.

"What do you want now?" he asked supporters.

He warned of a threat from neighboring NATO countries as well as from the opposition movement calling for new elections, as the crowd shouted "No!"

"If we kowtow to them, we will go into a tailspin and will never stabilize our aircraft," Lukashenko said.

"We will perish as a state, as a people, as a nation," he said, as security staff stood nearby with his teenage son Nikolai.

NATO later dismissed allegations by Lukashenko but said it was closely monitoring the situation.

"There is no NATO buildup in the region. NATO's multinational presence in the eastern part of the Alliance is not a threat to any country. It is strictly defensive, proportionate, and designed to prevent conflict and preserve peace," a NATO spokeswoman said in a statement.

During Saturday's phone call, the leaders of Russia and Belarus agreed that the problems in Belarus would be resolved soon, the Kremlin said.

Accused of rigging last Sunday's election, Lukashenko had earlier issued an appeal to the Russian president as the Belarusian leader grappled with the biggest challenge to his 26-year rule amid the threat of new Western sanctions.

Ties between the two traditional allies had been under strain before the election, as Russia scaled back subsidies to a country Russia sees as a strategic buffer against NATO and the EU.

Statements by both sides contained a pointed reference to a "union state" between the two countries. Lukashenko has previously rejected calls by Moscow for closer economic and political ties as an assault on his country's sovereignty.

"Both sides expressed confidence that all the problems that have arisen will be resolved soon," a Kremlin statement said after Lukashenko and Putin spoke by phone.

"These problems should not be exploited by destructive forces seeking to harm the mutually beneficial cooperation between the two countries within the framework of the union state," it added.

The EU is gearing up to impose new sanctions on Belarus in response to a violent crackdown, with at least two protesters killed and thousands detained.

On a visit to neighboring Poland, U.S. Secretary of State Mike Pompeo said Washington was monitoring the situation closely. The leaders of Estonia, Latvia and Lithuania called on Belarus to conduct new "free and fair" elections.

Lukashenko said he did not need foreign governments or mediators to solve the situation in Belarus, state news agency Belta reported. "We will not give the country away to anyone," he said.

Tens of thousands took to the streets of the Belarusian capital on Saturday. Crowds gathered to lay flowers where one of the protesters was killed earlier this week, waving flags and chanting anti-Lukashenko slogans.

(With input from agencies)