The Latest on developments in Syria (all times local):

11:40 a.m.

A relief group and Syrian opposition monitors say airstrikes have damaged and put of service one of the country's most secure hospitals, which had been dug into a mountain.

The International Union of Medical Care and Relief Organizations, or UOSSM, says the Dr. Hasan Al-Araj — also known as "Cave Hospital" and located in the central province of Hama — was struck twice on Sunday.

The Britain-based Syrian Observatory for Human Rights said on Monday that Russian warplanes carried out the attacks that hit the hospital near the central village of Kfar Zeita, adding that it's one of the largest hospitals in rebel-held areas of the country.

UOSSM said there were minor injuries from the attack.

Syrian and Russian warplanes have been blamed for a series of attacks that have damaged hospitals and clinics in rebel-held parts of Syria, mostly in the northern city Aleppo.

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11 a.m.

Turkish military officials say 15 Syrian opposition fighters have been killed in an ongoing battle with Islamic State militants in northern Syria.

The officials also say that about 35 Syrian rebels have been wounded in the fighting, which seeks to capture seven residential districts south of the town of al-Rai. According to a statement emailed Monday, "intense" clashes had taken place in the regions of Boztepe, Hardanah and Turkmen Bari.

The statement says the casualties took place over the last 24 hours.

Turkey sent troops and tanks into Syria in August to help Syrian rebels re-take IS strongholds near the border and curb the advance of Syrian Kurdish militia, which Ankara accuses of links with Turkey's outlawed Kurdish rebels.

Turkish officials spoke on condition of anonymity in line with regulations.