Three people were wounded here on Friday when a small bomb exploded opposite a hotel due to host an investment conference at the weekend, police said.
The chief minister of Balochistan Jam Mir Mohammad Yusuf called the blast in the city of Quetta an attempt to sabotage the meeting due to be held there on Saturday.
The Serena Hotel, where Prime Minister Zafarullah Khan Jamali had been expected on Saturday to chair a conference aimed at attracting investment to Balochistan, was not damaged.
Information Minister Sheikh Rashid Ahmed said Jamali had cancelled his plans to attend the conference before the blast due to party commitments in Islamabad, but Investment Minister Abdul Hafeez Sheikh would attend.
The blast occurred at a bicycle stand outside the Balochistan provincial court and opposite the Serena Hotel and the nearby Balochistan provincial assembly, which was in session at the time. Some windows in nearby buildings were shattered.
A hospital official said three men were being treated for injuries, one of whom a policeman was seriously hurt.
Quetta police chief Qazi Wahid said the blast was caused by a small time bomb attached to a bicycle.
Balochistan minister Yusuf berated police at the scene. "This is an attempt to sabotage the investment conference," he said. "This is not tolerable. It is a lapse on your part."
Balochistan is one of Pakistan's poorest regions and has been frequently troubled by Islamic militancy and tribal violence.
On Thursday, another small bomb exploded outside the ticket office of Quetta railway station, but caused no injuries.
On Monday, a car bomb exploded in the fishing town of Gwadar in the far south of Balochistan, killing three Chinese technicians working on a project to build a major seaport.
Police have detained 17 people in connection with that attack, which officials blamed on "terrorists". They have yet to make any formal arrest.
Local speculation has focused on Islamic militants opposed to the pro-US government, provincial nationalists angered at being sidelined from the project, or smugglers with connections to Iran who are concerned that the new port will cut into their business.
A little-known group, the Balochistan Liberation Front, phoned local newspaper offices in Quetta on Thursday to claim responsibility for the Gwadar bombing and vow more attacks.
Police said they could not say if the front had carried out the attack. It has claimed responsibility for past bombings in Quetta but authorities have not taken these claims seriously.