The US military has admitted that a misdirected airstrike in Syria killed 18 allied fighters after they were given the wrong coordinates by an associate force.
The strike was intended to target an Isis post near Raqqa but the Syrian Democratic Forces (SDF), a largely Kurdish group allied with the US, gave mistaken coordinates, Central Command said.
The SDF is currently attempting a campaign to capture the de-facto Isis capital of Raqqa and is working to free areas of north of the city from the militants.
A number of a organisations said differing numbers of fighters had died in the strike, from 17 to 25, with a local news agency says that funerals for fighters were being held in a border town.
The US took a more active role in the Syrian conflict last week when President Donald Trump ordered a missile strike on an Assad-regime airbase in response to an alleged chemical attack in the town of Khan Sheikhoun.
On Wednesday (12 April), Russia, an ally of Assad, vetoed a UN Security Council resolution condemning the use of chemical weapons in Syria. The resolution had contained a contentious paragraph calling for investigators to be given immediate access to the site of the incident.
The harrowing footage and the US's respsonse has put a new strain on relations between the US and Russia, with Secretary of State Rex Tillerson saying, during a trip to Moscow, that there was little trust on both side. Trump then went on to add, while standing next to Nato Secretary General Jens Stoltenberg, that the US is "not getting along with Russia at all".