Beirut: Syrian government forces carried out a series of air strikes on Wednesday on a city in southern Syria that has been declared a safe zone under a recent Russia-sponsored deal, opposition activists and an independent monitor said.

The Britain-based Syrian Observatory for Human Rights said government forces carried out at least 12 air strikes and dropped at least nine barrel bombs on rebel-held parts of Dara’a as intense clashes with rebels, including members of the Al Qaida-linked Levant Liberation Committee, continued in the city’s Manshiyeh neighbourhood.

The monitoring group added that at least two rockets were launched by government forces in the area.

The activist-run Step News Agency and Qasioun News Agency also reported clashes and shelling in the southern city.

Russia, Iran and Turkey agreed to establish the zones in Syria, signing on to a Russian plan under which President Bashar Al Assad’s air force would halt flights over designated areas across the war-torn country.

This week’s clashes are among the worst violations of the so-called de-escalation agreement.

Intense clashes in Dara’a began on Monday between government forces and rebels with both sides shelling parts of the southern city.

Dara’a, where protests against Al Assad’s rule first began in March 2011, is one of four “de-escalation zones” announced earlier this month during ceasefire talks in Astana, Kazakhstan.

Russia’s defence minister, meanwhile, said the deal to set up the zones is “the main document to end Syria’s civil war.”

Sergei Shoigu said Moscow has been discussing safe zones in Syria with several nations, including the United States, Israel and Jordan.

Shoigu said Russia has been working with Turkey and Iran to prepare for the deployment of a monitoring force to patrol safety zones once all the specifics are set at next month’s meeting in Astana.