The UN Security Council on May 19 strongly condemned what it called a "terrorist attack" on the Russian Embassy in Syria's capital.
Officials said a mortar round penetrated a diplomat's office and the building sustained "serious material damage," but no one was killed because people were out at lunch.
The attack came from the Jobar neighborhood, which is controlled by illegal armed groups, the officials said. The group responsible for the attack was not identified, however.
The Russian Embassy in Damascus has been targeted before. Russia is a strong ally of the Syrian government.
The U.S. State Department and Russian Foreign Ministry also condemned the mortar attack in separate statements.
"We call for those responsible for all such acts to be held accountable and continue to stress the need for a political solution to the turmoil in Syria," said department spokesman Jeff Rathke.
Based on reporting by AP and TASS