Three people have been killed and 12 others wounded after a bomb planted on a bicycle detonated in the southwestern Pakistani city of Quetta, local sources say.
Police officials in Balochistan province said the bomb was apparently detonated by remote control on Sunday, as a police van passed the scene.
Two policemen were among the dead, they said. The blast, which targeted a senior police officer, occurred on one of Quetta's main roads.
The officer was not in the car at the time, Hamid Shakeel, a police official, told the AFP news agency.
The vehicle was also badly damaged, he said.
There was no immediate claim of responsibility, but similar bombings have been blamed on secular tribal separatists in Balochistan.
Hundreds of people have died in attacks in the province since violence flared in late 2004, with Baluch fighters demanding political autonomy and a greater share of profits from the region's natural resources.
Balochistan has also been hit by attacks blamed on Taliban fighters and sectarian extremists.
|Tribesmen have accused the US and Pakistan of caring only about their internal issues [EPA]
The explosion in Quetta came a day after an umbrella group of aid organisations and political parties from Pakistan's semi-autonomous regions came out with a declaration calling for the army to crush the Taliban.
The statement was issued at the end of a meeting, attended by some powerful tribal leaders, on Saturday in the northwestern city of Peshawar.
Participants called for the army to escalate its attack against the network of fighters across the tribal regions, dismissing Pakistan's earlier offensives as "military dramas".
The participants also called for more power for traditional councils.
'Culture and tradition'
Tribal councils - or "jirgas" - play a central role in the Pashtun culture that dominates the region along the Pakistan-Afghanistan border.
These often-lawless regions, havens for al-Qaeda and Taliban fighters, have been the scene of bloody fighting and regular attacks by US drone aircraft as the Pakistani and US governments try to defeat the fighters who oppose the existence of foreign military on their countries' soil.
Smaller council meetings are used in tribal areas to decide matters ranging from local administration to criminal cases.
While Saturday's meeting was not a formal jirga, it is rare to have so many tribal leaders gather together.
'Sapling of terrorism'
A declaration at the end of the meeting called democracy vital to rooting out terrorism, arguing that Pakistan's powerful military - which many see as the true power behind the country's elected government - should keep out of politics.
"A sapling of terrorism cannot grow in democracy. Any attempt to derail democracy is like letting the terrorists walk all over us," the declaration said.
Participants said they had little faith in the US-Pakistan alliance, and that Washington and Islamabad were more worried about internal political issues than dealing with the social issues at the root of much of the violence.
A government offensive that began last year is is thought to have killed hundreds of people - both fighters and civilians - in South Waziristan.