A blast in the Battagram district in Pakistan's northwest is reported to have left at least six people dead.
Local media said the dead included three security personnel, two women and a child, while at least 10 others were severely injured.
Monday's explosion took place near an office of the Water and Power Development Authority, at the site where the Pakistan Muslim League-Quaid (PML-Q) party was to hold a gathering, addressed by its leader Amir Muqam.
"It is not clear whether it was a suicide attack or a planted device, but the target was definitely the public meeting," Khalid Khan Omarzai, a local administration official, told the AFP news agency.
President Asif Ali Zardari also confirmed the attack, reported Express 24/7, a local news channel.
Sources and witnesses said that a suicide bomber blew himself up when he was stopped by security personnel. Officials, however, have not confirmed this.
The injured have been taken to the local hospital, and police and law enforcement agencies have cordoned off the area. Forensic evidence is also being collected from the site.
Rescue teams were on their way to the site of the explosion.
The preparations of the gathering were underway when the blast took place and the PML-Q said it would continue with the procession.
Muqam has previously been attacked several times.
"We had informed the local administration some time ago and there should have been proper security arrangements in place," Muqam told Geo television, a Pakistan broadcaster, after the attack.