The United Nations Middle East peace envoy on Wednesday urged Israel and Palestinians to show restraint after a brief exchange of fire in which Israel bombed the Gaza Strip in response to Palestinian rocket fire.

“The United Nations condemns the indiscriminate firing of rockets into civilian areas and calls on Israel to act with restraint,” said Special Coordinator for the Middle East Peace Process Robert Serry in a statement. “It is of paramount importance to refrain from violence in this tense atmosphere and for parties to work constructively in addressing the underlying issues.”

Blaming rocket fire from Gaza and the tensions over unresolved issues of Palestinian prisoners held in Israel, Serry warned that the the situation was “volatile”. Serry noted that the UN will continue to support Egyptian efforts to maintain peace between Israel and Gaza terrorists.

Earlier in the day two rockets fired from Gaza exploded in southern Israel as air raid sirens sent residents of Sderot scrambling for cover. The missiles landed in open areas and caused no injuries or damage.

Overnight, Israel Air Force jets bombed areas in Gaza for the first time since November after Palestinian terrorists fired several mortar bombs and missiles at Israel earlier on Tuesday.

The exchanges of fire were the first since the IDF’s November 2012 Operation Pillar of Defense, which sought to bring an end to Palestinian rocket fire and concluded with a ceasefire agreement between Israel and Hamas, the group that controls the Gaza Strip.

“The renewed violations of the ceasefire risk undermining the ‘understanding’ reached between Israel and Gaza on November 21, and unraveling the gradual but tangible improvements achieved since then in the easing of the closure and the security situation in Gaza and southern Israel,” Serry said.

Shortly after the cross-border fire, the IDF announced that a fifth Iron Dome battery became fully operational on Wednesday. The battery, hastily brought into service during Pillar of Defense, successfully intercepted a missile fired at Tel Aviv during the conflict. In addition, a further two Iron Dome batteries were recently deployed in the north of the country. The IDF said the anti-missile batteries were positioned as part of a routine integration of the system into active service.

During the November fighting the Iron Dome system shot down hundreds of rockets fired at Israel by Palestinian terrorist groups in Gaza.