The blast came as armed forces and tribesmen battled Taliban fighters in various parts of the northwest region bordering Afghanistan. On Wednesday, tribesmen attacked Taliban hide-outs in Kurram tribal region, killing 28 militants and suffering seven fatalities themselves, officials said.
The roadside bombing occurred on Peshawar's outskirts, and the victims were taken to a hospital, senior police official Ghayoor Afridi said. No group has claimed responsibility, but Taliban militants have carried out numerous attacks targeting Pakistani security forces.
The fighting in the remote Kurram region was the latest in two weeks of battles between militants and tribesmen there that have killed 141 people, including more than 100 insurgents, two government officials said on condition of anonymity because they were not authorized to speak to media. Their accounts could not be independently verified.
Pakistan's leaders have encouraged local tribesmen in the semiautonomous areas close to the Afghan border to establish militias, known as lashkars, to flush out Taliban fighters blamed for attacks in the nuclear-armed country as well as in Afghanistan.
Such groups have been set up in several regions, but face stiff Taliban resistance.
Sajid Hussain Toori, a lawmaker from Kurram, said the militants were moving into Kurram from the Swat Valley, where the military is undertaking an offensive to root them out. He said hundreds of tribesmen took part in the attack early Wednesday, triggering a gunbattle that killed 28 militants and seven tribal fighters.
"Kurram is an important place because the Taliban can cross the Afghan border from here easily," Toori said. "The lashkar is facing these armed Taliban, but we request that the government send troops to Kurram to fight the Taliban as quickly as possible."
The fighting comes as Pakistani troops gear up for an offensive in South Waziristan, another part of the tribal belt where Pakistan's Taliban chief is believed to be based.
A poll released Wednesday appeared to mark a major shift in public support behind the government's ongoing offensive against the Taliban a campaign supported by the Obama administration, which believes security in Pakistan is vital to defeating the Taliban in neighboring Afghanistan.
The survey said that 81 percent of Pakistanis believe the activities of the Taliban and other Muslim extremists were a "critical threat" to the country, up from the 34 percent polled on the same question in September 2007.
Socio-Economic Development Consultants in Islamabad carried out the survey for WorldPublicOpinion.org, questioning 1,000 people across Pakistan from May 17 to 28, 2009. It gave a margin of error of plus or minus 3.2 percentage points.
This week, militants in North Waziristan announced they were pulling out of a peace pact with the government because of army operations in the northwest and continued U.S. missile strikes in the region. The collapse of the peace deal raises the likelihood that the army will have to wage an offensive in North Waziristan as well as South Waziristan.
Elsewhere in the northwest Wednesday, a roadside bomb targeting a local police chief exploded, killing a passer-by, police said. The incident took place in Dera Ismail Khan, a city near South Waziristan, said police officer Miran Shah.
Dera Ismail Khan has witnessed significant violence in recent years, some of it due to rivalries between Shiite and Sunni Muslims. Attacks on security forces in the region, however, tend to be blamed on Taliban militants.