At least 35 people have died after suicide bombers struck a bus carrying intelligence agency employees and a checkpoint near the headquarters of the Pakistan army.
The two attackers struck in Rawalpindi, a garrison city just south of the capital, Islamabad.
In the first attack, an explosive laden car rammed a bus carrying employees from the Inter-Services Intelligence agency, while the other bomber hit the checkpoint, said Mohammed Afzal, a local police official.
An intelligence agent at the scene said the destroyed bus was a 72-seater, but that more people were on board and it is thought the casualty numbers will keep rising.
After the blast, troops and police quickly blocked off the area of the blast.
They pushed back bystanders and snatched cameras and mobile phones from journalists and bystanders. Agents fanned out across the area, picking up metal bits of what appeared to be the suicide bomber's car.
It was the second major attack against the ISI in recent months.
On September 4, a suicide attacker blew himself up after boarding a bus carrying ISI's employees, while a roadside bomb went off near a commercial area in Rawalpindi minutes apart, killing at least 25 people.
Islamic militants have launched dozens of suicide attacks this year.
Most have taken place near the Afghan border, but several have taken place in the country's main cities, raising fears that violent extremism is spreading.
