At least seven people in Syria's Aleppo city were killed when the largest hospital in the rebel-held east was hit by a third air strike in a week.
The medical facility, known as M10, is "completely destroyed... It is gone", said Adham Sahloul of the Syrian American Medical Society on Monday, adding three maintenance workers were killed.
The attack killed another four people outside the hospital, Dr Abu al-Izz said.
The repeated attacks on hospitals in rebel-held Aleppo have drawn condemnation from the UN - and accusations of war crimes - and have led the US to threaten an end to its engagement with Russia over the conflict in Syria.
Al-Izz and Ibrahim al-Hajj of the White Helmets rescue organisation in eastern Aleppo said the hospital had been hit by a "bunker-buster" bomb - designed to demolish below-ground facilities - which, they said, are dropped by Russian planes.
Russia intervened in Syria a year ago to prop up President Bashar al-Assad's stumbling army.
Its air campaign has allowed government forces to reclaim territory from rebels and the Islamic State of Iraq and the Levant (ISIL also known as ISIS), most notably imposing a siege on eastern Aleppo where some 250,000 to 300,000 civilians are now trapped.
'Most secure hospital damaged'
Meanwhile, a relief group and Syrian opposition monitors said air strikes 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 (UOSSM) said on Monday the Dr Hasan Al-Araj Hospital in Hama province was struck twice on Sunday.
The Britain-based monitoring group Syrian Observatory for Human Rights said on Monday that Russian warplanes carried out the attacks, which hit the hospital near the central village of Kfar Zeita.
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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.
Source: News Agencies