London, Dec 1 (IANS): A British team secretly saved a Christian town in Lebanon from the advancing Islamic State (IS) forces by constructing a network of watch towers, a media report said.

The clandestine British squad worked at speed to coordinate the huge effort to build 12 towers along the border with Syria to prevent the forces of IS from "massacring" inhabitants of the town, the Telegragh reported Sunday.

The lookout points allowed the Lebanese army to stop IS militants storming west to the Mediterranean. It cut off the IS advancement into the small Christian town of Ras Baalbek, in the north of Lebanon.

British Prime Minister David Cameron took a close interest in the rescue of the village, the report said.

Tom Fletcher, the British ambassador to Lebanon, said he believed the watch towers helped prevent a massacre at Ras Baalbek, which could have led to a catastrophic destabilisation of the country.

The town is home to Druze, Sunni and Shia Muslims and two million Christians.

"They (IS) want these big symbolic victories -- you bust through a border, you carry out a massacre and you get the attention," Fletcher was quoted as saying.

"In a country that has such existing fragilities, that would have had dramatic consequences.”

The watch towers were constructed at high speed along the border, with each lookout made of six shipping containers welded together, the report said.

The former soldier who implemented the project estimated that Tango 10 -- the watch tower credited with stopping a massacre at Ras Baalbek -- had cost the British taxpayer 150,000 pounds ($235,000).

The watch towers were built in 17 days in July and finished less than two weeks before a major attack on the Lebanese border.

The attack involved thousands of fighters from IS and the Nusra Front, an Al Qaeda-affiliate based in Syria.