New York: Following the US decision to raise the terrorism alert, the United Nations has put its security officials on "high alert" and asked the staff to be vigilant while carrying out their normal routine.

Around 5000 staff at the UN headquarters have been asked yesterday (Dec 22, 2003) through email to remain vigilant by Assistant Secretary General Andrew Toh, who is in charge of security.

"Security officers in the United Nations have been placed on high alert and we seek the continued cooperation of staff and delegations in this regard," Toh said in the note.

The 39-storey United Nations headquarters is considered among the high profile buildings, which are vulnerable to terrorist attacks.

The world body's action follows the US decision of raising the level of terrorism threat from "yellow" to the second highest "orange", following intelligence reports about possibility of attacks by al-Qaeda network more severe than the Sept 11, 2001 ones during the holiday season.