The United States announced Wednesday it was ordering family members of US government employees and certain non-emergency personnel to leave Yemen.
The move by the State Department came amid calls for Yemeni President Ali Abdullah Saleh to step down and as fierce fighting between security forces and dissident tribesmen forced the closure of the airport in Sanaa.
"The Department of State has ordered all eligible family members of US government employees as well as certain non-emergency personnel to depart Yemen," it said in a travel warning.
It warned Americans "of the high security threat level in Yemen due to terrorist activities and civil unrest.
"The Department urges US citizens not to travel to Yemen. US citizens currently in Yemen should depart while commercial transportation is available," it said.
President Barack Obama earlier Wednesday repeated his call for Saleh to step aside as pitched battles were fought between tribal groups and security forces in Sanaa.
"We call upon President Saleh to move immediately on his commitment to transfer power," Obama said at a joint press conference with British Prime Minister David Cameron in London.
The State Department said the threats to security were also due to activities of terrorist groups including Al Qaeda in the Arabian Peninsula (AQAP), suspected of plotting and attemping to carrying out attacks on US soil
"The US government remains concerned about possible attacks against US citizens, facilities, businesses, and perceived US and Western interests," said the statement.
Saleh, who has been in power for 33 years, has since January faced protests calling for his departure from power, and recently refused to sign a Gulf Cooperation Council-sponsored accord that would have seen him cede power in exchange for immunity from prosecution.
In addition to months of anti-regime protests, the Al-Qaeda resurgence and now tribal battles with security forces, Yemen faces a southern secessionist movement and is battling a northern rebellion.
Follow Emirates 24|7 on Google News.