Unidentifiedgunmen have killed five African Union peacekeepers in the Darfur region ofwestern Sudan,the heaviest death toll suffered by the African force in one day since late2004.

Aspokesman said four soldiers were killed in the shooting and the fifth died ofhis wounds on Monday morning.

"Fourwere killed and one seriously injured while the attackers lost threecombatants," Nureddin Mezni said.

"Thisis the biggest number of (AU) casualties in one day since the African Union missionstarted operating," he said.

Helicopterunder fire

According to Mezni, Sunday's attack brought to 15 thenumber of AU troops killed in Darfur sincethey were first deployed.

Another soldier has been missing for months.

He gave no indication as to who might have been behindthe shooting.

A helicopter carrying AMIS' deputy commander wasattacked Saturday as it was on its way from Zalengei in western Darfur to the AMIS headquarters in El-Fasher. Nobody wasinjured.

Sunday's attack on the peacekeepers comes amidincreasing ethnic unrest in Darfur, where atleast 62 members of an Arab tribe were killed in an attack on Saturday.

The AU has 7,000 troops in Darfurbut is under-funded and ill-equipped.

Only one of three negotiating rebel groups signed apeace deal with the Khartoum government in Abuja in May last year.

The agreement has made little impact, with splintergroups involved in the renewed violence.

According to the UN, at least 200,000 people have diedand more than two million have fled their homes since the conflict began in February2003.