A Yemeni shot dead an American and a Canadian working at a Western oil firm in the Arab state on Tuesday and then killed himself, a Yemeni official said. Another Yemeni man was killed and a third Western man wounded in the attack, carried out by a carpenter working on the premises of the unnamed firm in the oil-rich Marib province, 105 miles east of Sanaa, the official said.

He identified the gunman as Naji al-Kumaim, in his early 40s, but gave no further details. "He killed himself after his act. The motive is not yet known," the official told Reuters.

The nationality of the wounded Westerner was not known.

U.S. firm Hunt Oil, the only oil firm operating in Marib, declined to comment on the incident.

An official at the Canadian embassy in Saudi Arabia, which is also responsible for Yemen, said the mission was aware of the incident but was not in a position to comment. The U.S. embassy in Sanaa said it would issue a statement.

Yemen is the ancestral home of Osama bin Laden , Washington's main suspect in the September 2001 attacks on U.S. cities, is seen by the West as a haven for Muslim militants and has arrested suspected members of bin Laden's al Qaeda network.

ANTI-WESTERN ATTACKS

Last December, a Yemeni gunman believed to have links to al Qaeda killed three U.S. missionaries at a hospital.

Last week, citing increased tensions in the Middle East, Canada warned its citizens not to travel to Yemen, where many people carry firearms.

"The heightened tensions as a result of the Iraq situation, together with increased threats globally from terrorism, put Canadians at greater risk," it said.

Yemen has seen some of the largest anti-U.S. protests in the Middle East, over the Iraqi and the Israeli-Palestinian conflicts.

In October, suspected militants attacked a French tanker off Yemen, about a year after suspected Qaeda members killed 17 U.S. sailors in an attack on the U.S. destroyer Cole.

A missile fired by a CIA unmanned drone killed six alleged al Qaeda members in Marib province in November, including a key suspect in the Cole attack.

Elsewhere in the Middle East, British Airways became the first airline to announce it was suspending flights to and from Tel Aviv after Britain's Foreign Office advised against all travel to Israel. It said flights would stop on Wednesday night.

A senior United Arab Emirates official said authorities were firmly in control of security, after the United States and Britain warned of possible terrorist attacks.

Lebanon said it was taking extra measures to protect Western assets and had boosted security in the south fearing Israel might use the cover of an Iraq war to attack.

PHOTO CAPTION

Thousands of demonstrators march through the streets of Sana'a, Yemen, Saturday, March 15, 2003. While shouting anti-American slogans, they carried pictures of Iraqi president Sadam Hussein, seen left, alongside pictures of the Yemeni president Ali Abdullah Saleh, and the national flag, right. (AP Photo/Bryant MacDougall)