According to initial reports, five to seven militants stormed the Jinnah Hospital in Lahore, killing at least twelve people and injuring ten more. A security guard and five police are among those killed. Militants entered the hospital in a rescue attempt to free the injured assailant of Sunday's attack on two Ahmadi mosques placed in intensive care, taking other patients as hostages.
I'll update the post as more information comes my way.
Update I: Hostage crisis is over and the Hospital has been secured. The militants escapes as the police entered, unsuccessful in retrieving the injured attacker. So far no single group has claimed responsibility, though an Al -Qaeda-Punjabi Taliban-Sectarian group nexus is thought to be responsible.