Tens of thousands of opposition supporters marched through Minsk Sunday, calling for an end to strongman Alexander Lukashenko's rule amid a heavy security presence and despite dozens of arrests.

Belarus protests have entered a third week since the disputed presidential election on August 9 in which Lukashenko claimed victory.

Meanwhile, opposition rival Svetlana Tikhanovskaya says she was the true winner.

An AFP journalist and local media estimated that more than 100,000 people attended Sunday's protest, equalling the scale of rallies on previous weekends, the largest in the country since independence from the former USSR.

A crowd gathered outside Lukashenko's official residence, the Palace of Independence, which was guarded by riot police and special forces personnel backed up by rooftop snipers.

Sunday's rally came on Lukashenko's 66th birthday and protesters carried quirky handmade "gifts" including a cardboard toilet with a sign urging the strongman to flush himself away, a coffin marked "Political corpse" and a picture of a cockroach, the opposition's nickname for the president.

Some laid flowers and symbolic gifts on the ground in front of a tall barrier manned by riot police equipped with helmets and shields.

This was the "boldest show of civil disobedience in three weeks of protests," opposition newspaper Nasha Niva reported.

- Lukashenko refuses to negotiate -

Activist Maria Kolesnikova, Tikhanovskaya's campaign partner, asked in vain to enter the residence for talks.

Presidential aide Nikolai Latyshenok came out to speak to protesters, but insisted Lukashenko would not negotiate with the opposition.

A Telegram messenger channel linked to Lukashenko's press service posted a picture of him in a bullet-proof vest holding a gun, and said it was taken at the palace as protesters were outside.

The protests began breaking up towards evening as heavy rain fell and people began leaving. Riot police also began to push protesters away from the palace.

Thousands of people attended similar rallies in other Belarusian cities, local media reported.

The Minsk Peace March started at 2:00 pm local time (1100 GMT) and police began to detain protesters almost immediately as people attempted to reach the central Independence Square.

Columns of protesters walked through the centre, carrying placards and the country's historic red-and-white flag as drivers honked car horns in support.

Some linked arms to march down a main street, while women took black-clad riot police to task or lay on the street in front of them.

One demonstrator, 33-year-old Nikolai, said he had already been detained after one demonstration and was still recovering from the beating he had received.

"Everything hurts," he said. "But I came out again for our Belarus to be free."

"We need to gather strength and come out like this every week until Lukashenko leaves," said another demonstrator, 70-year-old Maria.

The Belarusian interior ministry said police detained 125 people within the first two hours, Belta state news agency reported, most accused of taking part in illegal mass protests. Three were detained for damaging a police car, the ministry said.

Protesters faced off against armed interior troops and riot police using their shields to block them. Other protesters tried to bypass the police blockades.

Despite the heavy security, the atmosphere remained relaxed and festive.

Meanwhile, more than 360 Belarusian sports figures including Olympic athletes signed an open letter calling for new elections and condemning police violence.

- 'Morally bankrupt' -

The latest rally came amid a crackdown on media coverage.

On Saturday the foreign ministry withdrew accreditation for journalists from international media, including AFP, the BBC and Radio Liberty / Radio Free Europe.

A government official cited "counter-terrorism" grounds for the move, which was condemned by Germany and the United States.

A German government spokesman said Sunday they would summon the Belarus ambassador to the foreign ministry to protest the move.

Reporters covering the protests have been detained and police have confiscated memory cards from photographers' cameras.

The authorities have repeatedly shut off Internet access, making it harder for independent media to report from the demonstrations.

- Putin promises support -

European leaders have urged Lukashenko to establish a dialogue with the opposition, while Tikhanovskaya's supporters have set up a Coordination Council to organise a peaceful transfer of power.

Before Sunday's protests began, Lukashenko spoke to Russian President Vladimir Putin, who wished him a happy birthday.

The Kremlin said they agreed to meet in Moscow in the coming weeks and reaffirmed intentions to strengthen Belarus-Russian ties, after Putin this week vowed military support for Lukashenko if needed.

Three people have died during post-election protests and hundreds have been injured. More than 7,000 people have been detained.