Belarus confirmed the death of a jailed protester after police violently cracked down on demonstrations over disputed presidential polls.

The riot police have arrested thousands in street clashes across the country after long-serving leader Alexander Lukashenko claimed a landslide victory in Sunday's election.

The strongman's opponents accuse him of rigging the election where his main rival was a massively popular opposition candidate, Svetlana Tikhanovskaya.

The Belarusian Investigative Committee said in a statement that a 25-year-old man died after he was detained on Sunday in the southeastern city of Gomel and sentenced to 10 days in prison for taking part in illegal protests.

Investigators said the cause of death was unclear, while Radio Free Europe/ Radio Liberty earlier quoted the man's mother as saying he had heart problems and was held for hours in a police van.

Previously police said one protester died when an explosive device went off in his hand on Monday.

The latest death came as opposition protesters took to the streets to condemn police violence for the third day in a row.

In Minsk, several hundred women joined hands to form a human chain, many wearing white and holding flowers.

"The riot police are beating up people, brutally beating them, and all we can do is come out for such a peaceful protest," said one protester, 29-year-old advertising worker Darya. 

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UN High Commissioner for Human Rights Michelle Bachelet accused Belarus of deploying "unnecessary and excessive force."

French President Emmanuel Macron said he was "very worried" by the violence while US Secretary of State Mike Pompeo urged the European Union to "take action," saying: "We want the people of Belarus to have the freedoms that they are demanding."

Mr Lukashenko today dismissed the demonstrators as "people with a criminal past who are now unemployed" and told them to get jobs.

State television aired footage of detained young protesters with bloodied and bruised faces being asked if they wanted a "revolution".

Police are this evening readied for fresh protests, preventing pedestrians and vehicles entering central streets in Minsk while metro stations were closed, AFP journalists said.

The protests broke out after authorities said Mr Lukashenko, who has been in power since 1994, won 80% of the vote in Sunday's polls.

Last night saw smaller numbers on the streets than on previous days, after police cordoned off city centres and limited transport.

The interior ministry said protesters gathered in 25 cities and towns around the country and that more than 1,000 people were detained.

That brought the number of detentions to more than 6,000 after three days of protests.

In Minsk, protesters and witnesses said riot police used indiscriminate force against those gathered in various suburbs, firing stun grenades and rubber bullets. 

Police acknowledged opening fire on demonstrators and wounding one in the southwestern city of Brest on the Polish border. They said the protesters were armed with metal bars and ignored warning shots.

The protest movement arose in support of Ms Tikhanovskaya, a 37-year-old political novice who ran for president after potential opposition candidates including her husband were jailed.

The official results gave her 10% of the popular vote but Ms Tikhanovskaya said the election was rigged and claimed victory.

She left Belarus for neighbouring Lithuania yesterday as allies said she came under official pressure.

Ms Tikhanovskaya "is recovering from this stress... and feels better," Lithuanian Foreign Minister Linas Linkevicius told Russia's Echo of Moscow radio station.