United Nations Secretary-General Antonio Guterres on Monday strongly condemned the deadly suicide attack at Russian embassy in Kabul, capital of Afghanistan, which killed two embassy employees.

“The secretary-general strongly condemns today’s attack in Kabul in the immediate vicinity of the embassy of the Russian Federation. The secretary-general conveys his condolences to the families of the deceased and wishes a speedy recovery to the injured,” said Stephane Dujarric, spokesman for Guterres, in a statement.

The top UN official “reiterates that attacks against civilians and civilian objects, including diplomatic missions, are strictly prohibited under international humanitarian law,” the statement said.

Two employees of the Russian embassy in Kabul were killed as an unknown militant set off an explosive device near the diplomatic mission on Monday, the Russian Foreign Ministry said.

The explosion occurred at 10:50 a.m. local time (0620 GMT) in the immediate vicinity of the entrance to the consular section of the Russian embassy, the ministry said in a statement.

There were also victims among Afghan citizens, and the embassy is in close contact with the Afghan security services, which are investigating, it added.