The mother of Vladislav Kovalev on Saturday told the Belapan news agency that she had been informed in a letter of her son's death.

Lubov Kovaleva said that the document from the Supreme Court of Belarus informed her that the 26-year-old had been executed after an appeal for a presidential pardon was declined.

Kovaleva also shared the information with the right group Vyasna, which posted a scan of the letter on its website. It read "the sentence of your son Vladislav Kovalyov has been carried into effect."

The brief letter tells Kovalyova that she can collect a death certificate but it does not say that she will be able to collect her son's body.

"We will not stop. We will rehabilitate Vladislav," the AFP news agency reported his sister Tatyana as saying, adding that he had been shot. "God forbid that this happen again, that they shoot an innocent person."

There has been no official confirmation of the execution, and whether the second man convicted in connection with the bomb attack, Dmitry Konovalov, 26, had also been executed remained unclear.

The April 2011 nail-bomb blast at Minsk's busiest metro station, near the offices of strongman President Alexander Lukashenko, killed 15 people. The men were also found to have carried out bomb attacks in 2005 and 2008, injuring dozens.

On Thursday, the authoritarian president - who has ruled the ex-Soviet state for the past 18 years - rejected final appeals for clemency for the men.

There had been concerns as to whether the men's guilt had been proven beyond doubt during the trial.

The European Union on Friday urged Belarus not to carry out the executions and to put a moratorium on capital punishments. The same day, Germany entered an official appeal to stay the executions.

Belarusexecuted two convicts in 2011, according to data published by Amnesty International. The human rights organization believes some 400 executions have been carried out there since 1991.

rc/ncy (AFP, dpa, Reuters)