London, Jun 20 (IANS): At least 20 British militants are thought to have travelled to Libya to join the Islamic State (IS) terror group, intelligence officials said.

According to the Sunday Times, the 20 British jihadis are currently in Libya fighting with Islamist groups, some having travelled directly from British shores and others joining from Syria.

IS fighters have been pinned down in parts of Libya's Sirte since forces allied to the UN-backed Government of National Accord (GNA) launched an operation to dislodge them from the coastal city last month.

The city represents the last IS stronghold in the country, and British fighters loyal to the extremist group are believed to have taken up arms to help the group cling on to the area, the Daily Mail reported.

"It’s a worrying trend that around 20 of the British jihadis have travelled to Libya, and no doubt others will follow," an intelligence official said.

Officials estimate that IS has 5,000 fighters in Libya, most of them in Sirte.