The BBC's Syed Shoaib Hasan in Islamabad says that Monday's incident is the second attack against army medical personnel this year, and the first since general elections were held last week.

The army says that Gen Baig's driver and guard were also killed in the bombing.

The bomb was detonated outside an office of the government's national data registration agency, on a main road that was busy with traffic. At least 20 people were injured, the interior ministry said.

A suicide attack in Rawalpindi on 4 February left at least six dead

"The bomber was apparently on foot and as the car stopped on the main mall road, he hit it," senior city government officer, Irfan Ellahi, told Reuters news agency.

In the incident in Mansehra, attackers stormed the office of the British-run non-governmental organisation, Plan International, and fled in two cars after setting the premises ablaze.

At least 10 people were injured in addition to the four Pakistani nationals who were killed. Earlier reports said that six people had died.

Plan International - based in the south of England - has been active in the area for 12 years in the fields of education, health and development.

"We have immediately closed our operations across Pakistan and dispatched a security team to the area. Counselling will be provided for those affected by the tragedy," Plan International Chief Executive Tom Miller said.

He said a motive for the attack was unknown.

Hundreds of people have been killed in suicide attacks in Pakistan over the past year.

Our correspondent says that the attacks appear to be part of a campaign by pro-Taleban militants to target military personnel in retaliation for army operations in Pakistan's north-western tribal areas - said to be a safe haven for the Taleban and al-Qaeda.