British intelligence on Syrian troopmovements is helping rebels launch successful attacks on regime forces, a Sunday newspaper reported, quoting an opposition official.
The Sunday Times weekly said the disclosure by the official was the first indication that British intelligence was playing a covert role in the anti-regime revolt which first erupted in March 2011.
The newspaper quoted the official as saying British authorities "know about and approve 100%" intelligence from their Cyprus military bases being passed through Turkey to the rebel troops of the Free Syrian Army (FSA).
"British intelligence is observing things closely from Cyprus. It's very useful because they find out a great deal," the official told the newspaper. "The British are giving the information to the Turks and the Americans and we are getting it from the Turks."
According to the official, the most valuable intelligence so far has been about the movements of troops loyal to President Bashar al-Assad towards the flashpoint commercial hub of Aleppo, which is partly controlled by rebels.
The stricken second city has become the focus of the conflict, partly because of its strategic location near the Turkish border.
"The British monitor communications about movements of the government army and we got information about reinforcements being on their way to Aleppo," the official told The Sunday Times.
"We hit at the government troops in Idlib and Saraqib [southwest of Aleppo], with success."
The report said that early in August, FSA fighters had reported two large columns of government troops heading towards Aleppo.
One was from Latakia on the Mediterranean coast and the other from Damascus, the capital. The fighters did not reveal the source of their intelligence at the time.
"We ambushed troops and a column of more than 40 tanks in a valley near Saraqib," the official told The Sunday Times.
"We cut them off and destroyed many of them with repeat attacks with rocket-propelled grenades."
Britain has two sovereign military bases in Cyprus, one at Dhekelia and one at Akrotiri.
They draw intelligence from the airwaves for GCHQ, Britain's national electronic surveillance centre in Cheltenham, western England, the report said.