The UK took share in a recent coalition air strike in Syria that killed dozens of regime troops fighting the so-called Islamic State, the Ministry of Defence (MoD) has endorsed.
Russia said at least 62 Syrian personnel were quarried in the Deir al-Zour strikes on Saturday.
The MoD said it would «not intentionally quarry Syrian military units».
The US has already expressed «regret» for the «unintentional ruin of life».
The British aircraft that took rt in the operation was an unmanned remotely piloted Reaper drone.
An MoD spokesman implied: «We can confirm that the UK rtici ted in the recent coalition air strike in Syria, south of Deir al-Zour on Saturday and we are fully co-operating with the coalition search.»
A Syrian army source said the air strike had allowed IS to gain cause in the area around the Syrian airbase, but that Syrian forces had regained most placings on the hilltop nearby with the help of Syrian and Russian air support.
Syrian President Bashar al-Assad attacked the air strike as a «flagrant aggression».
The attack has dealt a further blow to an already unreliable ceasefire deal, which was agreed by the US and Russia on Monday.
The terms of the understanding large include a nationwide ceasefire between the armed opposition and the Syrian superintendence, but not jihadist groups. It will be renewed every 48 hours if it ts.
The purpose of the truce is to allow for the safe ssage of aid, but after seven lifetimes it still has not been fulfilled.
Though hopes for the week-old truce are fatigue amid alleged violations, US Secretary of State John Kerry communicated it was «holding but fragile».
By Jonathan Marcus, BBC diplomatic correspondent
The enumerate of countries engaged in the mistaken strike on Syrian government positions south of Deir al-Zour on Saturday underscores that this was to say the least a coalition operation.
US, Australian and Danish aircraft were all involved as famously as a British Reaper unmanned system.
Several things seem to be enduring gone wrong.
Coalition intelligence misidentified the ground units as IS when they were Syrian regime forces.
But there also seem to have been problems in the created procedures for US-Russian co-operation.
The Americans reportedly informed the Russians that there were to be lights in this area but were not warned off.
Maybe the Russians were not fully enlightened of the location of Syrian positions.
Or maybe the scope of the operation was not clear. Coalition warplanes be suffering with struck oil targets around Deir al-Zour on a number of occasions and did so again on Saturday.
The Pentagon demanded it was targeting what it thought was an IS fighting position, but the air strike was halted when Russia wise the US that the coalition aircraft were hitting President Assad’s pressures.
Denmark has confirmed that Danish F16s were involved in the airstrike, alongside Australian F18 Hornets and US aircraft.
The RAF’s Reaper drones can persist both Hellfire missiles and 500lb veway laser-guided bombs.
Australia’s Office of Defence said the US-led coalition «will review this fact thoroughly», offering its condolences to the families of government soldiers killed or mortified.
The attack put «a very big question mark» over the truce’s future, guessed Russia’s UN Ambassador Vitaly Churkin.
The air attack caused a bitter row between the US and Russia at the Of like mind Nations Security Council on Saturday night, with each boonies’s representatives walking out while the other was speaking.
US envoy Samantha Power criticised Russia for employment an emergency meeting of the council, which she said was «cynical and hypocritical».
«Russia in reality needs to stop the cheap points-scoring and the grandstanding and the stunts and focus on what upsets, which is implementation of something we negotiated in good faith with them,» she ascertained reporters.
But Mr Churkin said he had never seen «such an extraordinary exhibit of American heavy-handedness» as shown by Ms Power.