Protesters in Belarus have gathered outside a prison to mark the birthday of the jailed husband of the country's main opposition figure as anger mounts over a disputed election.

Sergei Tikhanovsky, who has just turned 42, was imprisoned alongside other rivals of President Alexander Lukashenko ahead of the 9 August poll.

His wife Svetlana Tikhanovskaya ran in his place but later fled to Lithuania.

She reportedly secured about 10% of the vote, and Mr Lukashenko more than 80%.

There were no independent observers. The opposition has held daily since protests over the past 10 days, alleging massive vote-rigging.

Hundreds of protesters have been wounded and two have died in clashes with police. Thousands have been arrested, and many have spoken of torture at the hands of security forces.

Mr Lukashenko, who has led Belarus since 1994, insists he has won fairly and has ruled out holding another election.

What happened on Tuesday?

Hundreds of opposition supporters gathered outside the jail in the capital, Minsk, where Mr Tikhanovsky is being detained on charges of inciting violence.

Many held red-and-white balloons - the colours of the opposition - and sang "happy birthday".

Ms Tikhanovskaya, 37, said her husband was spending his birthday in prison because of "a crime he did not commit".

"All of this blatant lawlessness and injustice shows how this rotting system works, in which one person controls everything, one person who has kept the country in fear for 26 years, one person who robbed Belarusians of their choice," she said in a video message.

Ms Tikhanovskaya says that where ballots were properly counted, her share of the vote ranged from 60% to 70%.

In another video message released on Monday, she said she was ready to become a "national leader" to restore peace and prepare for new elections.

How strong is the pressure on Lukashenko?

On Sunday, more than 100,000 people gathered in Minsk for the largest protest held in Belarus since it declared independence from the Soviet Union in 1990.

Strike action is also keeping up the pressure on the president. State TV and key factories have been affected and on Tuesday postal workers reportedly joined the strikes.

A number of officials, as well as current and former police officers, have resigned.

On a visit to a tractor plant on Monday, Mr Lukashenko defended the official election tally, telling workers: "We held the election. Until you kill me, there will be no other election."

But as he spoke, many in the audience booed him and chanted "leave".

The 65-year-old strongman - who has called the opposition "rats" - remains defiant.

He has maintained close relations with neighbouring Russia, on which Belarus heavily relies for energy supplies.

What's happening internationally?

EU leaders are to hold an emergency video summit on Wednesday. EU foreign ministers agreed last week to prepare new sanctions against Belarusian officials responsible for "violence, repression and the falsification of election results".

On Tuesday, German Chancellor Angela Merkel spoke to President Vladimir Putin of Russia. In a phone call, she said the Belarusian government must release political prisoners and start a dialogue with the opposition.

Mr Putin told Ms Merkel that foreign interference would only escalate the crisis.

On Monday, the UK said it did not accept the results of the "fraudulent" election and US President Donald Trump said his administration was following the "terrible situation" in Belarus closely.

President Lukashenko has sought Russian help, saying Mr Putin has promised to provide comprehensive assistance in the event of any external military threat.