Syrian rebels have captured an army base in the eastern province of Deir Az-Zor, striking another blow against President Bashar al-Assad’s military and further weakening his control in the strategic region bordering Iraq.

Thursday’s capture of the artillery base on the outskirts of Mayadeen, a town on the Euphrates river near some of Syria’s main oilfields, follows rebel takeovers of military installations in the north and centre of the country this week.

“The Mayadeen military base fell at 8:30 am (06:30 GMT),” Abu Laila, an official in the Military Revolutionary Council in the province, told Reuters news agency.

He said 44 rebel fighters had been killed in the siege of the base.

“The whole countryside, from the Iraqi border and along the Euphrates to the city of Deir Az-Zor, is now under rebel control.”

Another opposition source in contact with rebels confirmed that the base, 42km southeast of Deir Az-Zor, had fallen.

Farther north, battles raged in the town of Ras al-Ain on the Turkish border between rebel forces and Kurdish fighters linked to Turkey’s longtime foe, Kurdistan Workers’ Party (PKK).

The confrontation between the two groups is one of the largest so far in the coutry’s 20-month uprising.

Russian warning

In the face of the growing turmoil on its southern border, Turkey has asked its NATO allies to deploy surface-to-air Patriot missiles to protect its frontiers, but Russia spoke out strongly on Thursday against any such move.

“This would not foster stability in the region,” Alexander Lukashevich, Russian foreign ministry spokesman, said on Thursday.

NATO ambassadors met on Wednesday to consider the request, which followed weeks of talks between Turkey and its allies about how to shore up security on its 900km border to avoid a spillover from the Syrian civil war.

A deadly air strike hit near a hospital in al-Shaar neighbourhood in Aleppo

Laurent Fabius, French foreign minister, said in Paris on Thursday that France backed Turkey’s request.

“There is no reason to object, it is purely defensive,” he told BFM TV.

Turkey has repeatedly scrambled fighter jets along the frontier and responded in kind to stray shells flying into its territory during the conflict in Syria, where an estimated 38,000 people have been killed an uprising against Assad’s government began in March 2011.

On Wednesday evening, Syrian fighter jets flattened a building next to a hospital in Aleppo, killing at least 40 people, including a doctor who was in the middle of a surgery.

Once a private hospital, the Dar al-Shifa became a field clinic run by volunteer doctors, nurses and aides united by their opposition to the regime and the need to give medical care to both civilians and rebels.

The warplanes turned the building adjacent to the hospital into a pile of rubble and sprayed shrapnel and debris into Dar al-Shifa itself, activists said.