ISLAMABAD — Authorities Friday arrested the former head of a banned Sunni extremist group from a town in central Pakistan, less than a week after the organization claimed responsibility for a market bombing that killed 89 Shiites. Senior police officer Ashfaq Gujar said Malik Ishaq was arrested on government orders in the central city of Rahim Yar Khan. It was not immediately clear on what charges he was arrested, although Gujar said Ishaq had been sent to a high-security jail for investigation. Ishaq and his associates have been investigated in the past, and Ishaq himself was imprisoned for 14 years on charges, never proven, of killing Shiite Muslims. He was released in July 2011. Ishaq is one of the founders of Lashkar-e-Jhangvi, a group accused of killing hundreds of Shiites, who constitute some 20 percent of the population in the majority Sunni country. Most of the two groups live together peacefully, though tensions have existed for decades. On Friday, Mahdi Hasan, a leader of Hazara Democratic Party, welcomed Ishaq's arrest, but demanded the arrest of all others involved in the attacks. – AP