Ultra-conservative Islamists used bombs and a bulldozer to destroy the tomb of a 15th century Sufi scholar in the Libyan city of Zlitan, witnesses said on Saturday, the latest attack in the region on sites branded idolatrous by some sects.

The attackers reduced the revered last resting place of Abdel Salam al-Asmar to rubble on Friday and also set fire to a historic library in a nearby mosque, ruining thousands of books, witnesses and a military official added.

A Reuters journalist in Zlitan, about 160 km (90 miles) west of the Libyan capital, said the mosque's dome had collapsed and a minaret was pockmarked with holes.

The attackers appeared to have removed the last signs of the shrine with a bulldozer, which was abandoned nearby.

Libyan authorities have struggled to control a myriad of armed factions that have refused to give up their weapons following the revolution that ousted Muammar Gaddafi last year.

The latest destruction followed two days of clashes between tribal group in Zlitan which killed two people and injured 18, according to military council counts.

"The extremist Salafis took advantage (of the fact) that security officials were busy calming down the clashes and they desecrated the shrine," Zlitan military council official Omar Ali told Reuters, referring to conservative Muslims who see many Sufi sites as idolatrous.

Hardliners, emboldened and armed by the Arab Spring revolts, have targeted a number of sites sacred to Islam's mystical Sufi tradition in Libya, Egypt and Mali over the past year.

The assaults recalled the 2001 dynamiting by the Taliban of two 6th-century statues of Buddha carved into a cliff in Bamiyan in central Afghanistan.

Sufism is a mystical strain of Islam which includes hymns, chanting and dancing among its devotions.

Followers have built shrines to revered holy men and make pilgrimages to them. Even Gaddafi, with his ambivalent attitude to religion, did not try to interfere in a practice deep-rooted in Libyan culture.

Salafis believe Islam should keep to the simple, ascetic form practiced by the Prophet Mohammed and his disciples. Followers reject any later additions to the faith - including lavish tombs or grave markings.

A Facebook page titled "Together for the Removal of the Abdel Salam al-Asmar Shrine" congratulated supporters on the "successful removal of the Asmar shrine, the largest sign of idolatry in Libya." It posted photographs and YouTube footage of the destruction.

"We are distraught at the destruction of this historical and spiritual place in Libya," Mohamed Salem, caretaker of the mosque, told Reuters.

Salem said he had to flee Zlitan weeks ago after an increase of death threats against him from Salafis threatening to destroy the shrine.