US airstrikes on Syria's Raqqa in March 'hit school and marketplace', killing dozens of children

US airstrikes on a school and market in Syria's Raqqa province earlier this year killed at least 84 civilians - including dozens of children - Human Rights Watch said on Monday.

The killings highlight the high-cost of the US air war on Raqqa, with the campaign criticised by human rights groups for the number of strikes on densely-packed civilian areas.

Scores of civilians were killed following an air strike on a school for displaced children and a bakery situated in a market, Human Rights Watch said.

Although IS fighters were at the locations, so too were a a large number of civilians, the group said.

"These attacks killed dozens of civilians, including children, who had sought shelter in a school or were lining up to buy bread at a bakery," HRW Deputy Emergencies Director Ole Solvang said.

"If coalition forces did not know that there were civilians at these sites, they need to take a long, hard look at the intelligence they are using to verify its targets because it clearly was not good enough."

An airstrike on 20 March at the Badia school in Mansoura killed at least 40 people, including 16 children. The second strike at the Tabqa market and bakery on 22 March killed at least 44 people, including 14 children.

The US-led coalition has insisted it takes all measures to minimise civilian casualties, but the force has been criticised for the high number of deaths during the campaign.

Civilian deaths are believed to have increased during Donald Trump's tenure as president.

He is thought to have removed or relaxed some of the safeguards for pilots engaging IS fighters.

US-led coalition aircraft are supporting the mostly Kurdish Syrian Democratic Forces that are attempting to win back the last areas of the city still under Islamic State group.

Agencies contributed to this story.