At least four people have been killed and 14 injured in a suicide bombing at a naval college in the Pakistani city of Lahore, officials say.
Lahore's police chief said two attackers drove by motorcycle into the back entrance of the college and exploded separate bombs.
A number of blasts were heard - though officials said those may have been fuel tanks exploding on other cars.
It is the fourth apparent suicide attack in Pakistan in five days.
The country has been fighting an Islamist insurgency in its northern provinces and its major cities and military are frequently targeted by bombers.
Former Prime Minister Benazir Bhutto was killed by a suicide bomber in Rawalpindi in December.
On Sunday at least 40 people were reported killed in a suicide attack on a gathering of tribal elders in north-western Pakistan.
Lahore, the capital of Punjab province, has not been a frequent target, although 19 people were killed in a suicide bomb attack near the High Court in January.
Ms Bhutto's widower and the new leader of her party, Asif Ali Zardari, condemned Tuesday's attack as "inhuman, barbaric and most despicable".
Mr Zardari, who is leading attempts to form a coalition government following recent elections, called on Pakistanis to unite against "conspirators and extremists".
After Tuesday's blasts, television footage showed mangled gates, cars on fire, smoke billowing from the car park at the back of the Naval War College, and medics ferrying the dead and injured to ambulances.
The bombs mangled cars and blew a hole in the compound wall
Lahore police chief Malik Mohammad Iqbal said: "Two suicide bombers attacked the naval college."
He said the first drove up to the gate and destroyed it by exploding a bomb.
"He cleared the way for the second bomber to drive into the parking lot where he also exploded himself," he told the AFP news agency.
Medics were seen recovering the severed head and shoulder of a suspected bomber. The Naval War College is Pakistan's primary training school for senior officers.
It is located in the heart of Lahore, in a high-security area that also houses the state governor's house, a five-star hotel and government offices.