Germany, Australia and the Netherlands have joined Britain in urging their citizens to immediately leave the eastern Libyan city of Benghazi.
Officials have warned of a “specific and imminent” threat to Westerners staying there.
The alert follows the seizing of a gas facility by Islamist militants in neighbouring Algeria which left nearly 70 people dead.
Few Westerners are believed to be in Benghazi. Officials said the threats were directed at European nationals.
One local resident, Ayyoub Zayid said: “The departure of diplomats and the United Nations from Libya is a negative sign that shows how poor security is. We must all pay attention to this.”
Benghazi was a nerve centre for Libyan rebels in the uprising against Muammar Gaddafi. Since he was toppled, there has been a wave of violence against diplomats and security officials.
The most high profile was last September’s attack on the American embassy which killed the US Ambassador and three others.
The city has been the scene of power struggles between armed Islamist factions.