The secretary-general maintained that "diplomatic facilities must enjoy protection even in times of conflict," said UN Spokesman Stephane Dujarric at a daily news briefing on Wednesday, Xinhua reported.
Three diplomats were injured in a mortar shell targeting the Russian embassy in the Syrian capital Damascus Sunday as Syria promptly handed over a preliminary report of its chemical weapons in fulfillment of its commitment made earlier.
In the mortar attack, one shell was fired by militants in the hotspot district of Brazeh onto the Russian embassy compound. Brazeh has been a scene of fierce clashes raging on for days between the rebels and the Syrian government army.
An investigation is underway and additional steps are being taken with the help of the Syrian side to tighten security of the Russian diplomatic mission, reports said.
The Russian Embassy has been hit several times before by the opposition militants who are trying to overthrow the current Syrian government.