"The attacker wanted to go inside. He exploded himself when officials wanted to search his body,'' he said.
There was no immediate claim of responsibility.
Surge in violence
The complex at Kamra or its workers have been targeted at least once before.
In December 2007, a suicide car bomber struck near a bus carrying children of air force employees, wounding five of them.
The Kamra bombing follows a gun attack on a military vehicle on Thursday in Islamabad which killed a brigadier and his driver.
Two men had approached the vehicle on a motorbike and sprayed bullets at it before fleeing.
Millions of students have been kept at home this week as Pakistan shut all schools and colleges after a suicide attack on Tuesday at a university.
On October 10, fighters staged an ambush on the army headquarters in Rawalpindi. It was later claimed by the Tehreek-e-Taliban in Pakistan.
Almost three weeks of attacks by the Pakistani Taliban have left about 170 people dead.
The surge in violence comes as the military's offensive against the Pakistani Taliban in South Waziristan enters its seventh day.
Al Jazeera's Alan Fisher, in Islamabad, said: "Everywhere, as far as the Taliban is concerned, is a legitimate target if it involves the security forces, the police and the army.
"Everyone is wary of what will happen next and because of this the prime minister [Yusuf Raza Gilani] has summoned a special security meeting in Islamabad which will take place today.
| Exclusive report: Thousands flee South Waziristan as the conflict escalates
"He has summoned senior advisers and politicians, including representatives from the provinces and also people who can feed into the process, to see how they can try to cope with the problems that they are facing."
Gilani condemned the Kamra attack and vowed that the government would not waver in its resolve to "root out terrorism".
"They knew that when the South Waziristan offensive started that there was always the possibility of a backlash and that's what we are seeing," our correspondent said, referring to the Pakistani authorities.
"[The government] is aware that they have to do something, because people are scared. You can see it on the streets, in the fact that there is not as much traffic around as usual, that the markets are quieter, cinemas across the country are reporting that attendances are down.
"The army said earlier this week that their intention was to target what they described as the biggest bully in the neighbourhood.
"They believe that if they can confront and defeat the Taliban in South Waziristan, then other groups around the country will adapt to the new realities.
"It's a risky strategy. If it fails, it allows others to push on with their agenda and carry out attacks."