By Gul Yousufzai

QUETTA, Pakistan (Reuters) - A provincial official criticized Pakistani security forces on Sunday after a bombing targeting the Shi'ite Hazara community killed 80 people in the northwestern city of Quetta.

"The terrorist attack on the Hazara Shi'ite community in Quetta is a failure of the intelligence and security forces," Nawab Zulfiqar Ali Magsi, governor of Baluchistan province, said while touring a hospital.

"We had given a free hand to security (forces) to take action against terrorist and extremist groups, but despite that the Quetta incident took place."

The death toll from Saturday's bombing rose overnight to 80, with most of the casualties in the main bazaar of the town, capital of Baluchistan, near the border with Afghanistan.

Most of the dead were Hazaras, a Shi'ite ethnic group. A senior security official said the figure could rise as 20 people were critically wounded.

Pakistan's government, already unpopular over a range of issues such as poverty and power cuts ahead of elections expected in a few months, is under mounting pressure to go after hardline Sunni extremists who regard Shi'ites as non-Muslims.

A spokesman for Lashkar-e-Jhangvi (LeJ), a Sunni group, claimed responsibility for the bomb in Quetta, which also caused casualties near a school and a computer center.

LeJ has also said it was behind a bombing last month in Quetta which killed nearly 100 people, one of Pakistan's worst sectarian attacks.

Shi'ite political organizations have called for a strike in Quetta to protest against the latest carnage. Many shops and bazaars are closed. Relatives of the wounded responded for an appeal for blood made by hospitals.

Pakistani intelligence officials say extremist groups, led by LeJ, have escalated their bombings and shootings of Shi'ites to trigger violence that would pave the way for a Sunni theocracy in U.S.-allied Pakistan.

More than 400 Shi'ites were killed in Pakistan last year, many by hitmen or bombs. Some hardline Shi'ite groups have struck back by killing Sunni clerics.

The schism between Sunnis and Shi'ites developed after the Prophet Muhammad died in 632 when his followers could not agree on a successor.

(Reporting by Gul Yousufzai; Editing by Ron Popeski)