At least three people have been killed in the explosion of an improvised device in Quetta, the capital of southwestern Pakistan's restive Balochistan Province, despite heightened security as opposition parties held a large rally in another part of the city.
The leaders of an alliance of major opposition parties have held rallies in two other cities this month in a coordinated campaign to oust Prime Minister Imran Khan over his alleged failure in handling the country's economic crisis.
Two people were also wounded when the device planted in a motorcycle exploded on October 25 in a vegetable market that had largely closed for the day, said Azhar Akram, a senior police officer in Quetta.
No one immediately claimed responsibility for the attack.
The market was several kilometers from where the political rally was taking place. Local TV footage showed several vehicles on fire following the blast.
Mobile phone service in Quetta had been cut off as a security precaution ahead of the rally, and additional security patrols were deployed to patrol the city. Liaquat Shahwani, spokesman for the provincial government, said the opposition parties had been warned of the risk of violence.
Opposition leaders at the rally in Quetta voiced concern over the "enforced disappearances" of ethnic Baluch, which they say were orchestrated by the intelligence services.
Thousands of activists waving their parties' flags and banners were heard chanting " Go, Imran, go" as their leaders vowed to continue with their protests.
Earlier this month, militants in Balochistan killed 15 people when they ambushed a convoy of oil and gas workers escorted by paramilitary troops.
Balochistan, which is rich in gas and minerals, has been the scene of a low-level insurgency by armed groups demanding more autonomy and a greater share in the region's resources. Islamist militants also operate in the region.