Militants detonated four bombs in a heavily guarded Pakistani intelligence compound in the town of Sukkur on Wednesday and then fought security services, killing nine people and wounding at least 40, police officials said.
It was unclear who had carried out the attack, but previous similar operations have always been claimed by the Islamist Taliban, who appear to be throwing down the gauntlet to the new government of Pakistani Prime Minister Nawaz Sharif.
A gun battle raged for more than an hour as security services pursued up to 10 militants, Sukkur police Deputy Superintendent Masood Bangash said.
The city headquarters of the Pakistani military intelligence service, Inter-Services Intelligence (ISI), seemed to be the main target, police Deputy Inspector General Javeed Odho said.
A security official said seven attackers had been killed along with a civilian and an ISI employee.