U.S. Secretary of State John Kerry says Russia and Syria should face a war crimes investigation for their attacks on Syrian civilians.

Kerry says Syrian forces struck another hospital overnight, killing 20 people and wounding 100.

He says Russia and Syria owe the world "more than an explanation" about why they keep hitting hospitals, women and children.

Such acts, he says, "beg for an appropriate investigation of war crimes."

Kerry says such attacks are "way beyond" accidental at this point.

He accuses the pair of undertaking a "targeted strategy ... to terrorize civilians."

U.S. condemns Russia bombings as 'barbarism'

The U.S envoy to the UN in September called Russia's actions in Syria "barbarism," not counterterrorism.

Hundreds of people have been killed in bombings and many hundreds more wounded, with little access to treatment in hospitals that lack basic supplies.

A damaged field hospital room is seen after airstrikes in a rebel-held area in Aleppo, Syria, on Saturday. Rebels say Moscow and the Syrian army have for months been targeting power plants, hospitals and bakeries to force nearly 250,000 believed to be trapped in the city into surrender. (Abdalrhman Ismail/Reuters)

Rebels say Moscow and the Syrian army have for months been targeting power plants, hospitals and bakeries to force nearly 250,000 believed to be trapped in the city into surrender.

Russia joined the war a year ago, tipping the balance of power in favour of Syrian President Bashar al-Assad, who is also supported by Iranian ground forces and Shia militia from Lebanon and Iraq.