The station, Express 24/7, said 65 people were wounded and more than 20 houses destroyed. The attack took place in a village that opposes al Qaeda-backed Taliban insurgents, officials said.
They said the bomber struck as young men played volleyball in front of a crowd of spectators, including elderly residents and children, near the town of Lakki Marwat.
Local police chief Ayub Khan said the bomber blew himself up in an SUV in the middle of the field and there was believed to be a second vehicle which fled the scene.
One was blown up here while the second fled to an unknown location. We believe it may be used to attack some other place, he told Reuters by telephone.
An attack on a sporting event is highly unusual, although militants have started bombing crowded areas such as markets to inflict mass killings and spread fear and chaos. Officials said people in the village had formed an armed anti-Taliban militia, a phenomenon that started in Pakistan last year.
Despite major military offensives against their strongholds along the Afghan border, the Taliban have killed hundreds of people in bombings since October, challenging pro-American President Asif Ali Zardari, who already faces political heat because corruption charges against his aides could be revived.
Khalid Israr, a senior regional official who spoke by telephone from a hospital treating blast victims, said people recalled seeing the bomber drive a vehicle on to the playing field just before the explosion.
The bombing occurred on a day of strikes in the southern city of Karachi to denounce violence in Pakistan, an ally Washington needs to help stabilise Afghanistan.Pakistan's commercial capital Karachi nearly shut down in a strike called by religious and political leaders after a suicide bomber killed 43 people at a Shi'ite procession on Monday. The Taliban claimed responsibility and threatened more violence.
In a sign of growing anxiety over security, the United Nations will withdraw some of its staff from Pakistan because of safety concerns, a U.N. spokeswoman said on Thursday.
On a visit to Karachi on Friday, Interior Minister Rehman Malik said militant groups were harming Pakistan. They are hired assassins. They are enemies of Pakistan. They are enemies of Islam, he told reporters.
While many Pakistanis object to the violence, they are also frustrated with Zardari's inability to stabilise the nuclear power.
Militants have become increasingly brazen in their bid to topple his government and impose their brand of Islam, including public floggings and executions for anyone who disobeys them.
The Taliban has extended its reach from its strongholds to major Pakistani cities, including an attack on a mosque near the headquarters of the powerful military.
Karachi's streets were nearly empty on Friday. The stock exchange,, which normally operates on the first day of the year, was closed. Security forces carried out patrols. But residents were taking no chances.
We are already losing business and can't take the risk of going out today and opening our shops, said Saleem Ahmed, who sells electronics at one of the city's markets.
(Additional reporting by Faisal Aziz in Karachi; Writing by Michael Georgy; editing by Andrew Dobbie)