An air strike has hit a refugee camp in northern Syria, near the border with Turkey, killing and wounding dozens of people, Syrian pro-opposition activists said.

US defence secretary Ash Carter has said an American air strike that may have killed a number of Iraqi soldiers seems to have been “a mistake that involved both sides”.

A US military investigation has concluded that air strikes against an Islamic State checkpoint in Iraq in March probably killed four civilians, possibly including a child.

Doctors Without Borders has called for an independent and unprecedented fact-finding mission to investigate a US air strike on a hospital run by the medical aid group in Afghanistan that killed at least 22 people.

The deputy leader of the so-called Islamic State militant group has been killed in a US military air strike in Iraq, a spokesman for the Obama administration said.

Pakistani air strikes have killed 65 militants in two tribal regions along the Afghan border, the army said.

More than 20 people have been killed, many of them children, and dozens wounded in air strikes on a town in northern Syria held by the so called Islamic State, activists said.