DAMASCUS/BEIRUT (Reuters) - Rocket attacks killed 10 people in Damascus on Thursday and wounded at least 50, a monitoring group said, in the second heavy bombardment by Islam Army insurgents in less than two weeks.
The Syrian Observatory for Human Rights, which monitors violence in Syria, also said the army had responded with at least 40 air strikes in the Eastern Ghouta district, where Islam Army is based, and that 57 people had been killed.
Islam Army was formed by a merger of rebel factions in 2013. It follows an Islamist doctrine and has in the past received backing from Saudi Arabia.
Syria's state news agency, SANA, said five people had been killed in what it said was a bombardment by "takfiri terrorists". "Takfiri" is a term used to describe hardline Sunni groups who consider other people infidels.
SANA made no mention of army air strikes on Eastern Ghouta.
A witness in Damascus heard more than 30 blasts in quick succession and said they appeared to come from shells fired from the east.
The radio station Sham FM said the projectiles had hit at least five areas. Images posted on social media were said to show plumes of smoke rising above the city.
A message on a Twitter account thought to belong to Islam Army chief Zahran Alloush said the attack was a taste of what the Syrian military had done to Ghouta. He described Damascus as a "military zone" this week, and said his group would respond to air force strikes.
SANA showed photographs of damaged cars and buildings and wounded people being treated in hospital. State television said three missiles had hit areas around the ancient Umayyad Mosque, located in the capital's Old City.
Around 200,000 people have been killed since 2011 in Syria's civil war, which pits President Bashar al-Assad against a range of rebel groups including Islamist brigades and hardline jihadists such as Islamic State and al Qaeda's Nusra Front. U.S-led forces are bombarding Islamic State in both Syria and Iraq.
Elsewhere on Thursday, the air force attacked areas northeast of Damascus including the city of Douma and the town of Arbin, killing 35 people and wounding around 140, the Observatory said.
A video posted by the media arm of rebel fighters in the south showed huge clouds of smoke rising between buildings in what a voiceover said was Douma.
On Jan. 25, Islam Army mounted one of the heaviest attacks on Damascus in over a year, firing at least 38 rockets and killing seven people, the Observatory said.
On Sunday in Damascus, a bomb claimed by the Nusra Front tore apart a bus carrying Lebanese Shi'ite Muslim pilgrims.
Reporting by Mariam Karouny and Sylvia Westall; Editing by Kevin Liffey