At least 20 people have been killed and 70 injured in a suspected car bombing in the north-western Pakistani city of Peshawar, police say.
The blast hit a heavily populated area outside a Shia mosque near the central Kissa Khwani bazaar.
It was not immediately clear who was behind the attack.
Recent violence in north-west Pakistan has included sectarian clashes as well as fighting between the army and Islamist militants.
The attack in Peshawar ripped through the bazaar, where people were shopping ahead of the Muslim festival of Eid.
Women and children are believed to be among those killed, and a number of people were said to be trapped under rubble.
The identity of the victims was not immediately clear. A local resident said militants quickly cordoned off the scene.
The officials spoke on condition of anonymity because they are not authorized to speak on the record to media.
THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.
PESHAWAR, Pakistan (AP) _ A car bomb devastated a busy street in northwest Pakistan on Friday, killing at least 20 people, injuring scores more and unnerving a region already dangerously on edge after the attacks on India's commercial capital last week.
Escalating violence is destabilizing Pakistan's northwest just as the country faces accusations from archrival India that the gunmen behind the carnage in Mumbai were trained in Pakistan and steered by militants based there.
Neither the motive nor the culprits behind the Friday evening blast in Peshawar were clear. But provincial government chief Haider Khan Hoti said "external forces" could be to blame _ a comment understood in Pakistan to mean India.
The bomb went off near Peshawar's famed Storytellers Bazaar early Friday evening, wrecking a Shiite Muslim mosque and a hotel and setting a string of vehicles and shops ablaze.
Mohammed Bilal, a 28-year-old goldsmith being treated at a city hospital for a gash on his face, said he saw a white van explode in the street as he was walking home.
"Something struck me in face, and I fell down. There was fire and smoke and the cries of the injured people," Bilal told an Associated Press reporter.
Television footage showed survivors frantically carrying bloodied victims through the rubble to private cars and ambulances as fire crews sought to douse the flames.
Khizer Hayat, a senior doctor at the city's main hospital, said 20 bodies as well as over 60 wounded people were brought there.
Police chief Malik Naveed Khan said the bomb seemed to contain chemicals designed to spread fire.
While police were guarding government and religious buildings, "it is not possible to prevent this kind of terrorism unless you have extremely credible information," he said.
Pakistani forces have stepped up operations against Taliban and al-Qaida strongholds in the northwest from where militants have been mounting attacks in both Afghanistan and Pakistan.
Insurgents have responded with a campaign of gun and bomb attacks that have raised concern that they could cut a key supply line for NATO and U.S. troops through the Khyber Pass into Afghanistan.
There has also been a rash of kidnappings and attacks on foreigners in the northwest, including the Nov. 12 shooting death of a U.S. aid worker in Peshawar.
Earlier Friday, a suicide car bomber killed six people at a checkpoint in the Orakzai tribal region, just south of Peshawar, after police and local tribesmen waved for him to stop.
In the nearby town of Bannu, police said militants armed with guns and rockets killed two officers manning another checkpoint.
Militants recently vowed to step up attacks on Pakistani forces in retaliation for cross-border U.S. missile strikes into the region, which is considered a likely hiding place for al-Qaida chief Osama bin Laden.
The region is also bedeviled by sectarian tensions between extremists from the majority Sunni Muslim community and minority Shiites, and mosques have been repeatedly targeted in what officials say are tit-for-tat attacks.
The United States is seeking to calm tension between Pakistan and India, nuclear-armed neighbors who have fought three wars, in part to ensure that Islamabad remains focused on fighting militants in the northwest.
But Hoti, the provincial leader and a member of the party in the federal coalition government, pointed to "elements" in the lawless tribal belt who "act at the behest of external forces" when asked who carried out the attack in Peshawar.
"In today's tragic incident, the possibility of external involvement is very much there," he said.