BERLIN: Al-Qaeda is plotting to kidnap German and British citizens in Libya, the Spiegel weekly magazine quoted German intelligence sources as saying.

Germany and Britain were among several Western countries to urge their nationals to leave the eastern Libyan city of Benghazi on Thursday, days after a deadly attack by Islamist militants in neighbouring Algeria.

Britain cited a "specific and imminent" threat to Westerners in Libya's second largest city, but officials declined to give any details.

Spiegel, citing sources in the German Federal Intelligence Service (BND), said on Sunday Al-Qaeda and other militant Islamist groups were specifically preparing attacks on British and German citizens in the area.

It gave no further details and the BND declined to comment.

On Thursday, German Foreign Minister Guido Westerwelle described the situation in Benghazi, cradle of the uprising that ousted Libyan dictator Muammar Gaddafi in 2011, as "serious and delicate" but also declined to provide any details.

The call to leave Benghazi irked Libyans, keen to win foreign investment to rebuild their fractured infrastructure and boost the oil industry after the revolution against Gaddafi.

Few Westerners are believed to be in Benghazi, which has experienced a wave of violence against diplomats as well as military and police officers, including an attack in September that killed the U.S. ambassador and three other Americans.

At least 38 hostages were killed in an attack on Algeria's In Amenas gas complex near the Libyan border earlier this month. The launch of France's military operations in Mali has also cranked up tensions in North Africa.