One of the two men accused of organizing a deadly subway bombing in the Belarusian capital Minsk last year, Vladislav Kovalyov, has been executed by shooting, his mother said on Saturday.
"I have received a notification saying the verdict had been fulfilled," Lyubov Kovalyova told reporters in Minsk.
President Alexander Lukashenko has refused to pardon the men despite calls by Western governments and rights groups not to carry out the death sentence. Belarus is the only nation in Europe still using capital punishment.
The fate of the other man, Dmitry Konovalov, is unknown.
The attack on April 11, 2011, killed 15 people and wounded hundreds of others.
Konovalov and Kovalyov were convicted of the attack in November last year.
Lyubov Konovalova said the letter, from Belarus' Supreme Court, is dated March 16.
She maintained that her son had been innocent, and accused the Belarusian authorities of attempting to "pin their crimes on our children."
In a ruling last year, the court described the two men as "explosive enthusiasts" and said they posed an "exceptional danger to society."