A hospital supported by Médecins Sans Frontières in Homs has been partially destroyed in a “double-tap” barrel bombing, a signature tactic of the Syrian air force.

The strikes on the hospital in Zafarana, a besieged town in northern Homs, killed seven people including a young girl, MSF said in a statement, and prompted the movement to nearby field hospitals of many wounded, some of whom died on the way.

Saturday’s strikes were the latest in an apparent pattern of escalating attacks on medical facilities and doctors in the Syrian civil war, according to human rights organisations.

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MSF, which operates and supports a number of health centres and field hospitals in Syria, said the attack bore the hallmark of a double-tap strike, whereby the first bombing is followed by a second one after paramedics have arrived to help the victims. “This double-tap tactic shows a level of calculated destruction that can scarcely be imagined,” said MSF’s director of operations, Brice de le Vingne.

MSF said a barrel bomb was dropped from a helicopter on a populated area of Zafarana at 9.40 am on Saturday, followed nearly an hour later by two barrel bombs at the entrance of the hospital, wounding 47 patients and medical staff in total. The attack is the third on an MSF facility in two months. In October, an MSF hospital in Kunduz, Afghanistan, was all but destroyed by US airstrikes, killing 30 people including 13 medical staff in what the organisation called a blatant breach of international law. Later that month, an MSF-run hospital in the northern Yemeni province of Sa’ada was destroyed in a missile strike.

Medical staff and facilities are coming under increasing attack in Syria as the civil war nears the five-year mark. Physicians for Human Rights, a New York-based organisation, said it documented 16 attacks on medical facilities in Syria in October, making it the deadliest month on record for medical staff. Ten of the attacks were carried out by Russian warplanes, and five were conducted by either the Syrian or Russian air forces, the organisation alleged.

Moscow has conducted several airstrikes in Syria since it launched a military intervention in early October aimed at shoring up the regime of President Bashar al-Assad, which had endured a series of military setbacks after a manpower shortage debilitated its army. Many towns in northern Homs are held by rebels who oppose the Assad regime and have been repeatedly bombed by both Damascus and Moscow. A barrel bomb is an improvised explosive device packed with TNT and other material and dropped manually from planes and helicopters. Its inaccuracy has led some observers to conclude that its use is a de facto war crime.

A report released in May by Amnesty International on the use of barrel bombs in Aleppo concluded that they had killed 3,000 civilians and 35 fighters between January 2014 and March 2015. The weapons had killed more than 12,000 people throughout the country from their deployment in 2012 until the date of the report’s release.

The report outlined the use of double-tap strikes in Aleppo, and activists and local journalists have documented similar attacks on medical facilities, markets and mosques.

“MSF once again reiterates its call that all efforts should be taken by all parties to the Syrian war to avoid civilians and civilian infrastructure, including hospitals and ambulances,” the organisation said. “The multiplication of these atrocious attacks, with overwhelmingly high numbers of civilians, including women, children and medical staff, wounded or killed, must cease.”