British forces took part in a coalition air strike which the Syrian government claims left dozens of its troops dead at the weekend, the Ministry of Defence has confirmed.
A MoD spokesman said they were "fully co-operating" with the coalition investigation into what happened.
The US military has already accepted it may have unintentionally struck Syrian troops while carrying out a raid against Islamic State forces on Saturday.
Russia has warned that the strike by coalition aircraft - which it said killed at least 62 soldiers - has put the fragile ceasefire in Syria at risk.
"We can confirm that the UK participated in the coalition air strike south of Dayr az Zawr on Saturday, and we are fully co-operating with the coalition investigation," the MoD spokesman said.
"The UK would not intentionally target Syrian military units. It would not be appropriate to comment further at this stage."
It is understood that the UK participation in the strike involved an unmanned Reaper drone.
The statement came as Denmark disclosed that two of its F-16 fighters jets also took part in the raid, while Australia has said that its aircraft were also involved.
The incident led to sharp exchanges between Russia and the US, with Moscow saying the strike was "on the boundary between criminal negligence and direct connivance with Islamic State terrorists".
There were fears that it could scupper an agreement between the two superpowers to co-ordinate air strikes against IS and al Qaida-linked militants if the ceasefire holds for seven days.