BEIRUT/AMMAN (Reuters) - Warplanes bombed rebel-held towns east of Damascus on Wednesday, striking residential areas where Russia had declared a ceasefire less than 24 hours earlier and leaving dozens injured, according to residents, rebels and a monitoring group.

Air raids and artillery hit three towns in Eastern Ghouta, part of Syria’s Damascus province, the Syrian Observatory for Human Rights said. A ceasefire had been agreed in the area until March 20, Russia’s Defence Ministry said on Tuesday.

The Syrian air force struck at jihadists linked to a former al Qaeda offshoot in Irbeen, a city north-east of Damascus in Eastern Ghouta, and in al Qaboun, closer to the center of the capital, according to a media unit of Hezbollah, a Damascus ally. There was no immediate comment from the Syrian military.

At least 30 air raids hit the region on Wednesday, along with dozens of artillery rounds and ground-to-ground missiles fired from government-held areas, a rebel and a resident said.

The Syrian army has been closing in on eastern suburbs of Damascus still in rebel hands, such as Qaboun, and seeking to storm neighboring towns in Eastern Ghouta. Air raids and fighting have escalated in recent days, opposition sources said.

The army and its allies are trying to force rebels to agree to truces similar to those that have led to the evacuation of thousands of opposition fighters to northern Syria.

The army has for the last 20 days concentrated its air strikes on Qaboun district, effectively ending a ceasefire that rebels in the area agreed with the Syrian army which had been in place since the end of 2013.

The army suspects tunnels from Qaboun to Eastern Ghouta have become a lifeline for people and rebels in the besieged area, the opposition’s largest remaining stronghold near Damascus.

“If they take over Qaboun, the regime will be able to enforce a complete siege of Ghouta,” said a fighter from Failaq al Rahman, a rebel group operating in the area called Fahed.

Thousands of civilians have fled Qaboun, a district that had drawn tens of thousands of people escaping from violence elsewhere. They have found refuge in the adjoining Damascene district of Barza, where many families have taken refuge in the streets, public gardens and mosques.

Barza has agreed a full truce with the government that has been in place since 2014. Unlike other besieged suburbs, most of civilians living in Barza can go to the capital to work and to buy food and other supplies.

Before the Syrian conflict began in 2011, more than half a million people lived in Eastern Ghouta. The sprawling mix of urban districts and farmland was once a major economic hub serving the capital, but now its population has dwindled to tens of thousands and continues to shrink.