Police in the Pakistani city of Quetta say they have arrested a key suspect behind two major sectarian attacks on the Shia community in Balochistan.
The two bomb blast caused chaos in Quetta
They say that the suspect, known only as Habibullah, helped plan attacks on a Shia mosque in July 2003 and on a Shia mourning procession in March 2004.
A total of more than 100 people died in the two incidents.
Police allege that the man is a key leader of the banned Sunni militant group, Lashkar-e-Jhangvi.
Police say that Habibullah - who was arrested in a raid - is suspected of masterminding some 30 attacks against Shiites.
"This is a major success, and police are also trying to capture other associates of Habibullah," provincial police chief Chaudhary Mohammed Yaqub told the Associated Press news agency.
Pakistan has a history of sectarian violence between extremists from the majority Sunni and minority Shiite strands of Islam.
Police say their investigations have revealed that about 32 activists were involved in such attacks in Balochistan in recent years.
Of these only about four or five people were "key figures", and most are still eluding the authorities.
At least 50 people died and dozens were injured in July 2003, when suspected Sunni militants attacked a Shia mosque with grenades and guns in Quetta, the capital of Balochistan province.
In March the following year, suspected Sunni militants struck a religious procession of Shias in Quetta, throwing grenades and shooting worshippers before blowing themselves up in an attack that killed 42 people and injured 100.