Najaf, Aug 3, (VOI) – Unidentified gunmen assassinated an aide of top Shiite cleric Grand Ayatollah Ali al-Sistani near his home in the northern part of Najaf on Thursday night, an official security source said.

"Three gunmen in a vehicle assassinated Sheikh Fadel al-Aql, a deputy of Sistani, in the neighborhood of al-Milad, (11 km) north of Najaf at 10:00 p.m. on Thursday," the source told the independent news agency Voices of Iraq (VOI) on Friday.

The security source did not give further details about the incident. He said security agencies were "conducting intensive investigations" into the assassination.

The assassination is the fourth of its kind in two months in which assistants of the senior Shiite cleric were targeted.

Sehikh Abdullah Falak, a prominent Sistani aide who was in charge of financial duties in the cleric's office was stabbed to death inside his office in Najaf a couple of weeks ago.

The assassination set off concerns in political and religious circles as the area where he was killed was only 50 meters away from Sistani's heavily-guarded residence. The police said they arrested the culprit but have not revealed his identity.

A few days later unidentified gunmen assassinated Kadhem al-Bederi, the former official in charge of protecting al-Rawda al-Haydariya, the mosque of Imam Ali, the most sacred figure for the Shiites, on the Kufa-Najaf highway. Bederi was one of Sistani's guards before he assumed the responsibility for protecting the shrine.

Two months ago, on June 6, gunmen assassinated Sheikh Rahim al-Hassanawi, a representative of Sistani, in the district of al-Mishkhab, south of Najaf province, in front of his home in al-Jazirah neighborhood, 8 km north of Najaf.