A lone gunman has shot and killed three Americans in a Christian missionary hospital in Yemen.

A fourth American was badly injured in the attack in the southern town of Jibla.

ATTACK VICTIMS

Martha Myers, 54, from Alabama - killed William Koehn, 60, from Texas - killed Kathleen Gariety, 53, from Wisconsin - killed Donald Caswell, 49, from Texas - seriously injured

The gunman was arrested and said he carried out the attack for his religion. Officials say they believe he is a member of a local Yemeni group, Islamic Jihad.

Investigators will also look for any connection to Osama Bin Laden's al-Qaeda network.

Though mainly Muslim Yemen has co-operated with Washington's "war on terror", Islamic militants in the country have launched repeated attacks on Western targets.

US and Yemeni forces also carry out operations against suspected al-Qaeda members. A CIA drone fired a missile which killed six suspected militants in Yemen last month.

Meeting massacre

The gunman was said to be cradling his Kalashnikov rifle inside a jacket like a child and posing as a patient or relative as he entered the hospital in Jibla, about 170 kilometres (105 miles) south of the capital, Sanaa.

Donald Caswell was shot in the stomach

He went into a room where staff were holding a morning meeting and opened fire.

Hospital administrator William Koehn, purchasing agent Kathleen Gariety and doctor Martha Myers were killed by shots to the head.

The attacker then went to the hospital pharmacy and shot pharmacist Donald Caswell. Surgeons removed bullets from Mr Caswell's stomach and reports say he is expected to recover.

Officials identified the arrested gunman as Ali Abdulrazzak al-Kamel, from Damar province.

Mr Kamel told police that he had carried out the attack to "cleanse his religion and get closer to Allah", unnamed Yemeni officials told the Reuters news agency.

He is a student at Yemen's al-Iman university - which was briefly closed last year after allegations that it was a hotbed of Islamic militancy.

The president of the Southern Baptist Convention, Jack Graham, called the murdered workers "martyrs".

The Baptists - a Christian denomination - have run the hospital for 35 years. The president of the Baptists' International Mission Board, Jerry Rankin, said representatives there were not "over-Christian" in their work.

He said missionaries would continue working at the hospital, despite increased warnings from US officials.

Punishment promised

President Ali Abdullah Saleh sent a message of condolence to his US counterpart George W Bush, expressing shock and outrage at the attack on people who were working to help Yemenis.

RECENT VIOLENCE

December 2002: Senior Yemeni opposition politician, Jarallah Omar, assassinated November 2002: CIA unmanned plane kills six alleged al-Qaeda members October 2002: Attack on French tanker, the Limburg, blamed on al-Qaeda October 2000: USS Cole attacked in Aden, killing 17 US sailors. Attack blamed on al-Qaeda

"The authors of this hateful crime will not escape punishment and will be punished by justice so they can serve as examples to others" he wrote in the statement carried by the official Saba news agency.

"We are in the same trench in fighting terrorism and drying up its resources because it is a scourge that threatens peace and security in the world."

The White House denounced the killings. A State Department spokesman said it had been a "despicable attack" and welcomed the arrest of the suspect.

The US embassy in Sanaa has sent a team to help investigate the attack.

Relatives say the victims were committed to Yemen and their work there.

Dr Myers had been in Yemen for 24 years, her father told the Associated Press news agency.

Ms Gariety's brother Jerome told the agency: "We tried hard to get her to stay home [but] she wouldn't hear of that.

"I didn't want her to go, but I think what really took her back was the children. She loved the children," he added.

Al-Qaeda activity

Since the 11 September 2001 attacks, Yemen has been cracking down on suspected al-Qaeda members in an attempt to shed its image of being a haven for Islamic militants.

The US believes al-Qaeda members went into hiding in Yemen after the collapse of the Taleban in Afghanistan last year.

Al-Qaeda has been blamed for two attacks off Yemen's coast - the French tanker Limburg was attacked in October, two years after 17 US sailors died in the bombing of the USS Cole.