Television footage showed damaged buildings and ambulances at the scene
A gun and bomb attack on an office of Pakistan's main intelligence agency in the central city of Multan has killed at least 12 people, police say.
More than 25 others were injured when suicide attackers opened fire. A rocket was launched during the attack and grenades were also thrown.
The violence came a day after bombings killed about 60 in Lahore and Peshawar.
More than 400 people have been killed during a string of attacks mounted by Islamist militants in recent weeks.
They coincide with an army offensive targeting the Taliban stronghold of South Waziristan in the country's north-west.
Police said there were multiple attackers in Multan, two of whom were suicide bombers.
The blast caused massive destruction
They said one had a rocket launcher and fired into the local offices of Pakistan's main ISI intelligence agency and that others hurled grenades before setting off a huge explosion.
The building was severely damaged. Emergency workers say 12 people were killed but there are warnings the number of dead may well increase.
No-one has yet said they were behind the attack.
A senior police officer in Multan, Agha Mohd Yusuf, told the BBC that two to three attackers had arrived at their target in a car.
One of the attackers stepped out when the car reached a check point for the military area on Qasim Bela road.
"He put a rocket launcher on his shoulder and fired in the general direction of the office. One building was hit and collapsed," Mr Yusuf said.
"In the confusion that followed, the other attackers drove inside and blew up the car. This time the office of the intelligence service [Inter-Services Intelligence or ISI] agency was hit."
The attack in Multan is the latest in a number of commando-style attacks in Pakistan in recent months.
There have also been almost daily bombings across the country.
Monday was the bloodiest day for some weeks, with twin blasts in a packed marketplace in Lahore coming hours after a suicide attack outside a court in the north-western city of Peshawar.
Overnight, the death toll from the bombings in Lahore rose to 49. Scores more were injured in the blasts and the subsequent fire which swept through the market.
The Peshawar attack killed at least 10 people.
RECENT MILITANT ATTACKS IN PAKISTAN
Multan, 8 December: Intelligence agency office attacked - at least 12 killed
Peshawar: Many recent attacks - 28 October bombing killed about 120
Lahore: Targeted several times - market bombs killed 50 on 7 December
Rawalpindi: Several recent attacks, including one at a mosque on 4 December in which 35 died
Islamabad: Security tightened after series of attacks - 20 October bombing killed nine at International Islamic University
Charsadda, 10 November: Car bomb kills 34 and wounds 100