Alyaksandr Zhylnikau and Vyachaslau Sukharka appear to appeal their death sentences at the Supreme Court in Minsk on May 30.
The European Union and the Parliamentary Assembly of the Council of Europe (PACE) have strongly condemned the reported secret executions of two Belarusians whose appeals had been rejected by the country's Supreme Court.
"Two new executions in Belarus, of Viktar Liotau and Alyaksey Mikhalenia, have reportedly taken place in secret in mid-May 2018," the EU foreign-policy chief's spokeswoman, Maja Kocijancic, said in a statement.
In January, the Minsk-based Vyasna (Spring) human rights center said Liotau was sentenced to death in September 2017 for murdering his cellmate in a penal colony in Hlybokaye, some 160 kilometers north of Minsk.
Mikhalenia was sentenced to death in 2016 for murdering his neighbors, Vyasna said, adding that his appeal to the Supreme Court had been rejected.
"The continued application of the death penalty runs counter to [Belarus's] stated willingness to engage with the international community, including the European Union, on the matter and to consider the introduction of a moratorium on its use," Kocijancic said in her statement.
She also voiced concern for the death sentences for murder handed down earlier this year to two other Belarusians, Vyachaslau Sukharka, and Alyaksandr Zhylnikau.
Kocijancic said the sentences were upheld on May 30 by the Supreme Court.
Kocijancic warned that "tangible steps taken by Belarus to respect universal human rights, including on the death penalty, are key for shaping the EU's future policy towards Belarus," and reaffirmed the EU's strong and unequivocal opposition on capital punishment.
Yves Cruchten, general rapporteur of PACE on the abolition of the death penalty, and Andrea Rigoni, former PACE rapporteur on Belarus, also condemned the executions, saying that "the secrecy surrounding the execution of the death penalty in Belarus is a particularly disturbing feature."
Cruchten and Rigoni urged the Belarusian National Assembly to "consider this issue as a matter of urgency and move towards a moratorium on the executions without further delay."
Amnesty International, in its annual report on the capital punishment around the world published last month, noted that it was "particularly concerning" that no notification is being given to family members.
"The families of the prisoners only find out about the executions when they go to the prison expecting to visit or to leave parcels for the [detained] relative," Amnesty said.
Belarus remains the only country in Europe and Central Asia to carry out the death penalty.
In 2017, two people convicted of rape and murder, Syarhey Vostrykau and Kiryl Kazachok, were executed by shooting. The two were put to death in secret, in May and October, respectively, Amnesty said.