BEIRUT U.S.-led forces hit Islamic State bases in eastern Syria on Friday and a monitoring group said the Syrian army had intensified its bombing campaign in the west.
U.S. and Arab forces began bombing Islamic State militants in northern and eastern Syria on Tuesday, prompting concern among Western-backed opponents of Syrian President Bashar al-Assad that the air campaign could play into his hands.
On Friday U.S. Central Command, which has also been bombing bases of the al Qaeda splinter group in Iraq since last month, said it had destroyed more than a dozen Islamic State vehicles in both countries in its latest round of strikes.
The Britain-based Syrian Observatory for Human Rights, which monitors the conflict through a network of sources, said the Syrian army targeted areas held by a variety of insurgent groups, including Western-backed rebels.
Syrian warplanes used projectiles, including barrel bombs, in Hama, Idlib, Homs and Aleppo provinces and around Damascus, the Observatory said.
Five people were killed when barrel bombs were dropped on al-Rastan city in the Homs province and nine died in a barrel bomb attack east of Aleppo city, it said.
U.S.-led strikes early on Friday hit Islamic State bases and positions on the outskirts of the city of al-Mayadin in Deir al-Zor province, the Observatory said.
The U.S. Central Command said it had destroyed four Islamic State tanks and damaged another in three airstrikes south and southeast of Deir al-Zor.
The monitoring group said an earlier air strike hit the al-Tanak oilfield area in the province, while apparent missile strikes -- also thought to be carried out by U.S.-led forces -- hit the al-Quriyah area, also in Deir al-Zor.
U.S. Central Command has said Bahrain, Jordan, Saudi Arabia the United Arab Emirates and Qatar have participated in or supported the strikes in Syria since they began on Tuesday.
Strikes also hit areas southeast of the city of Hasaka, close to Syria's border with Iraq. They targeted Islamic State, al Qaeda's Nusra Front and other Islamist militants, the Observatory said.
Deir al-Zor, which borders Iraq, is almost entirely controlled by Islamic State militants and was a major oil-producing province before Syria's conflict began more than three years ago.
Oil has been a top source of revenue for Islamic State militants, and air raids on Thursday targeted refineries controlled by the group. The strikes also have seemed to be intended to hamper Islamic State's ability to operate across the border with Iraq, where it also control territory.
The Observatory said there were casualties from the earlier strikes but did not give details.
Centcom said airstrikes overnight and early on Friday in Iraq had destroyed Islamic State armoured vehicles south and southwest of Kirkuk and west of Baghdad. France has joined air strikes in Iraq and a string of other European countries have said they will follow suit.
(Reporting by Alexander Dziadosz and Sylvia Westall in Beirut and Susan Heavey in Washington; editing by Dominic Evans and Philippa Fletcher)