A leading suspect in a deadly attack on a Shiite Muslim mosque in July is related by marriage to Al Qaeda (searchterrorist Ramzi Yousef (search), convicted in the 1993 bombing of the World Trade Center in New York, police said.

The suspect, Daud Badini, also is believed to be a member of Lashkar-e-Jhangvi, an outlawed Sunni militant group implicated in a series of deadly attacks on Christians in Pakistan and on members of the country's Shiite minority, provincial police chief Shoaib Suddle said late Friday.

Badini remains at large, but four other suspected Lashkar-e-Jhangvi members have been arrested in connection with the July 4 attack.

Gunmen armed with assault rifles and hand grenades stormed the mosque in Quetta when it was crowded with about 2,000 people gathered for Friday prayers. About 50 worshippers were killed and hundreds wounded.

Two attackers were killed in a shootout with guards. A third was killed by his own grenade.

"During investigations it was found that Daud Badini is a brother-in-law of Ramzi Yousef, an active Al Qaeda member," said Suddle, who is the provincial police chief.

He said Badini's sister is married to Yousef, who is serving a life sentence in the United States for the 1993 attack, which killed six people and wounded more than 1,000.

The four other suspects in the mosque attack were identified as Shamim Ahmed, Mohammed Qasim, Abdul Waheed and Mohammed Jan. It was not clear when they were arrested.

In 2001, President Gen. Pervez Musharraf banned Lashkar-e-Jhangvi along with several other militant groups in a move aimed at eliminating religious extremism in the country.