GENEVA, March 11 (Reuters) - Entire families including

women and children were killed in Syria's coastal region as part

of a series of sectarian killings by rival groups, the U.N human

rights office said on Tuesday.

Pressure has been growing on Syria's Islamist-led government

to investigate after reports by a war monitor of the killing of

hundreds of civilians in villages where members of Assad's

minority Alawite sect lived.

"In a number of extremely disturbing instances, entire

families - including women, children and individuals hors de

combat - were killed, with predominantly Alawite cities and

villages targeted in particular," U.N. human rights office

spokesperson Thameen Al-Kheetan said, using a French term for

those incapable of fighting.

He said initial reports indicated that the perpetrators, who

have not been identified, were both members of armed groups

supporting Syria's interim authorities and those associated with

the former government.

"They appear to have been carried out on a sectarian basis,

in Tartus, Latakia and Hama governorates - reportedly by

unidentified armed individuals, members of armed groups

allegedly supporting the caretaker authorities' security forces,

and by elements associated with the former government."

So far, the U.N. human rights office has documented the

killing of 111 civilians and expects the real toll to be

significantly higher, Al-Kheetan told a Geneva press briefing.

Of those, 90 were men; 18 were women; and three were children,

he added.

"Many of the cases documented were of summary executions.

They appear to have been carried out on a sectarian basis...,"

Al-Kheetan told reporters. In some cases, men were shot dead in

front of their families, he said, citing testimonies from

survivors.

UN human rights chief Volker Turk welcomed an announcement

by Syria's Islamist-led government to create an accountability

committee and called for those investigations to be prompt,

thorough, independent and impartial, the spokesperson added.