Evacuation orders ... Most Western countries have advised citizens not to travel to the Libyan port city of Benghazi since September but now they are being advised to leave.

Evacuation orders ... Most Western countries have advised citizens not to travel to the Libyan port city of Benghazi since September but now they are being advised to leave. Photo: AFP

LONDON: Australia has joined Britain, Germany and the Netherlands in urging its citizens to immediately leave Benghazi after London warned of a ''specific and imminent threat'' to Westerners in the Libyan city where a US ambassador was killed in an attack in September.

Britain's warning sparked an angry response from Libya's government, which said there was ''no new intelligence'' to justify such concerns in the eastern city that was the cradle of the uprising that ousted dictator Muammar Gaddafi in 2011.

We acknowledge that there are security problems in Benghazi ... but there is no new intelligence that could justify this reaction. 

The alert out of London came just hours after the British Prime Minister, David Cameron, warned that last week's deadly attack on a gas complex in Algeria was only one part of what would be a ''long struggle against murderous terrorists'' across the world.

Glass, debris and overturned furniture are strewn inside a room in the gutted US consulate after an attack that killed four Americans, including Ambassador Chris Stevens.

Deadly attack ... the gutted US consulate in Benghazi after an attack that killed four Americans, including Ambassador Chris Stevens. Photo: AP

''We are now aware of a specific and imminent threat to Westerners in Benghazi, and urge any British nationals who remain there against our advice to leave immediately,'' the Foreign Office in London said in a statement.

Australia's Department of Foreign Affairs and Trade issued a similar alert on Friday morning.

''All Australians in Benghazi should leave immediately,'' DFAT said on its website.

The department reminded Australians that its travel advisory for Libya was still at its highest ''do not travel'' level ''due to the high threat of terrorist attack, the ongoing threat of kidnapping and the unpredictable security situation throughout the country''.

Germany and the Netherlands echoed the warnings in almost identical statements.

Libya's Deputy Interior Minister, Abdullah Massoud, expressed his ''astonishment'' at the warnings and said his country would be demanding an explanation from Britain.

''We acknowledge that there are security problems in Benghazi and that there have been for several months, but there is no new intelligence that could justify this reaction from London,'' the minister said.

''On the contrary. We are now in the process of establishing our authority in the east and in all of Libya, and the security forces are organising themselves little by little and are more and more visible on the ground.''

Agence France-Presse, AAP