At least one person has been killed after a suicide bomber on a motorcycle blew himself up near a bus carrying workers from a nuclear facility in the Pakistani city of Rawalpindi, police say.

Nasir Durrani, the city's police chief, had originally said that up to six people were killed in Thursday's attack, but later revised that figure down.

"About 25 people were on board and, as the bus reached a square, a motorcyclist hit its fuel tank," he said.

The bus was carrying workers from a main nuclear facility, the Khan Research Laboratories, Rao Iqbal, a police officer, said.

Pakistan has been hit by a wave of bombings in recent weeks in response to a military offensive against Taliban fighters in the northwest of the country.

But Thursday's was the closest to the capital since the launch of the offensive.

Rawalpindi, near Islamabad, is home to the headquarters of the Pakistani army and other state agencies.

Peshawar bomb

In a separate incident, a roadside bomb exploded as a police patrol passed by on the outskirts of the northwestern city of Peshawar, killing two policemen and wounding four, including two civilians, Safwat Ghayur, a senior police officer, said.

Commenting on the day's violence, Imran Khan, Al Jazeera's correspondent, said: "We are hearing of a number of attacks today.

"This battle with the Pakistani Taliban is a shooting war.

"The Pakistani military is under immense pressure to rout the Pakistani Taliban.

"Afghanistan's Taliban can go into Pakistan as easily as Pakistan's Taliban can go into Afghanistan. Co-ordination is the absolute key to all of this."