The release of Malik Ishaq, a leader of the banned extremist group Lashkar-e-Jhangvi, underscores the difficulty Pakistani prosecutors have convicting suspects in a justice system that lacks resources, is plagued by corruption and is rife with tales of witness intimidation. Ishaq was arrested in 1997, and has been accused of a slew of crimes, including attacks on Shiites. In 2009, he also was blamed for orchestrating the attack on the Sri Lankan cricketers in the eastern Pakistani city of Lahore. Six security officers and a driver died in that assault.

Although he’s been implicated in some 44 cases, he was convicted in just two minor ones, and has already served the time for those, said his lawyer, Qazi Misbah. But prosecutors have tried to keep Ishaq behind bars, even as they’ve struggled to prove other cases and persuade frightened witnesses to testify. Ishaq told Pakistan’s private Geo TV channel that he had been falsely accused.

In Karachi, meanwhile, the government ordered hundreds of extra paramilitary policemen onto the streets on Thursday after a fresh night of political and ethnic violence killed 15 people.

Late Wednesday, Zulfiqar Mirza, a senior member of the ruling Pakistan People’s Party, called Altaf Hussain, chief of the city’s powerful Muttahida Qaumi Movement, a murderer and an extortionist. He also maligned the city’s Urdu-speaking community that makes up the MQM party’s main base. Karachi echoed with gunfire soon after a local TV channel aired Mirza’s comments. Angry mobs also torched more than a dozen vehicles.

Mirza apologized for his comments Thursday, calling members of the Urdu-speaking community his “brothers.” His mea culpa came as thousands of people rallied in the center of the city to condemn him and burn his effigies. Hussain, who lives in self-imposed exile in London, appealed to his supporters to call off protests, which seemed to help calm the situation by Thursday evening.