Belarus President Alexander Lukashenko has said that Russia's Vladimir Putin has offered to help ensure the country's security, as opposition protesters keep up the pressure on the veteran leader over his claim to have won re-election.

Thousands of opposition supporters gathered in the capital today at the spot where a demonstrator died during this week's police crackdown on protests against Mr Lukashenko's claim to have won re-election last Sunday.

With the opposition gaining momentum after days of demonstrations, Mr Lukashenko's main election challenger Svetlana Tikhanovskaya has asked supporters to rally over the weekend.

Demonstrators laid flowers at the spot where Alexander Taraikovsky, 34, died on Monday. The crowd chanted "thank you" and raised victory signs while police kept a low profile.

Many held up photographs of protesters beaten during the crackdown, while one man stood in his underwear revealing the purple bruises on his thighs, buttocks and back.

Thousands protested outside the Belarusian state television centre, complaining that their broadcasts backed Mr Lukashenko and gave a skewed picture of the protests.

Riot police later arrived at the building and blocked off the entrance to the building.

Facing the biggest challenge to his rule since taking power in 1994, Mr Lukashenko called in Moscow's help and spoke on the phone with Mr Putin, after warning there was "a threat not only to Belarus".

A policeman checks participants' documents at a rally outside the Belarusian Embassy in Yekaterinburg

He later told military chiefs that Mr Putin had offered "comprehensive help" to "ensure the security of Belarus".

The Kremlin said the leaders agreed the "problems" in Belarus would be "resolved soon" and the countries' ties were strengthened.

While Mr Lukashenko periodically plays Moscow off against the EU, Russia is Belarus's closest ally and the countries have formed a "union state" linking their economies and militaries.

Mr Lukashenko issued criticisms of Russia during his election campaign and Belarus detained 33 Russians on suspicion of planning riots ahead of polls.

Opposition protesters criticised Mr Lukashenko for now seeking Moscow's aid and said they fear a Russian intervention.

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US Secretary of State Mike Pompeo has urged Mr Lukashenko to "engage with civil society" while visiting Poland today, which has offered to act as a mediator.

The opposition is planning a major show of force tomorrow with a "March for Freedom" through the streets of central Minsk.

Ms Tikhanovskaya, a 37-year-old political novice who ran after other opposition candidates including her husband were jailed, accuses Mr Lukashenko of rigging the vote and has demanded he step down so new elections can be held.

Svetlana Tikhanovskaya

The 65-year-old has ruled the ex-Soviet country with an iron grip and claims to have won the election with 80% of the vote.

Ms Tikhanovskaya left the country on Tuesday for neighbouring Lithuania, with her allies saying she came under official pressure. She has called for a weekend of "peaceful mass gatherings" in cities across the country.

She is also demanding authorities be held to account for the crackdown, which saw police use rubber bullets, stun grenades and, in at least one case, live rounds to disperse protesters, with at least 6,700 people detained and hundreds injured.