Iraq's No. 1 Shiite spiritual leader Grand Ayatollah Ali al-Sistani escaped an assassination attempt Thursday afternoon, a staff from his office confirmed.

Earlier, Al-Jazeera TV reported that a group of unidentified gunmen opened fire on Sistani's car as the cleric was leaving his office for home, but the attack failed to hurt Sistani.

A spokesman of Sistani said the spiritual leader is now safe and sound.

The attack came just one day before a team of UN experts was expected in Baghdad to assess the feasibility of Sistani's demand for elections to Iraq's first post-occupation government, which is due to be installed before July 1 of this year.

UN Secretary General Kofi Annan gave the green light for the trip after Washington called for the UN to intervene in a potential crisis with Sistani.

Sistani opposes a US plan to select a transitional assembly through a regional caucus system ahead of a 1 July deadline for transfer of power from the US-led occupation to an Iraqi authority.

He has been insisting on direct elections, but Washington maintains that nationwide elections in Iraq are not possible and has so far refused to budge on the handover date.