Media playback is unsupported on your device Media caption The bombing happened at a busy market, as Mike Wooldridge reports

A deadly bomb blast has struck a busy market on the outskirts of Pakistan's capital, Islamabad, killing at least 20 people, police and medics say.

The high intensity blast at the fruit and vegetable market left as many as 100 injured, reports say.

The Pakistani Taliban denied involvement. No other group has said it carried out the attack.

There is currently a ceasefire between the Pakistani Taliban and the government as part of peace efforts.

Analysis The Pakistani Taliban (TTP) chose to condemn the market bombing in more unambiguous terms than in the past. Their aim may well be to counter those who insist that a military operation - not peace talks - is the only way of dealing with the country's militants. Still, questions will be raised over where the TTP's true heart lies, given a clear undertone in their statement that attacks such as this latest one are the handiwork of the "hidden hand" - Pakistani secret agencies who they say are out to paint the TTP in a bad light. Many will also be sceptical about the militants' newfound concern for civilian lives - not too long ago the TTP routinely owned up to bombings that have killed thousands of civilians in recent years. Most independent analysts believe the militants see peace talks as a way of preventing military strikes against their hideouts, while elements within the wider militant network continue to chip away at the resolve of the Pakistani state to eliminate their sanctuaries. Continued militant attacks are likely to strengthen this impression.

Prime Minister Nawaz Sharif condemned Wednesday's bombing.

In comments released by his office, he said it was an effort by Pakistan's enemies to destabilise the country, but that the government would remain resolute in its efforts for peace.

Visiting the scene, Interior Minister Chaudry Nissar told the BBC the attack was "a dastardly act by criminals against some of the poorest people in the community". He said it was too early to know who was behind it.

Crater

Reports from hospitals in the area say as many as 100 people were injured.

The bombing happened in the Sabzi Mandi area of the capital about 08:00 local time (03:00 GMT), one of the busiest times of day for the wholesale fruit and vegetable market.

As a steady stream of casualties arrived at the two main hospitals nearby, reports of the number of dead and injured climbed and an appeal was made for blood donations.

Police said about 5kg (11lb) of explosives were hidden in a fruit box.

The BBC's Mike Wooldridge, at the scene, said the bomb left a deep crater in the thick concrete in the fruit section of the wholesale market, with boxes of guavas scattered all around.

Eyewitnesses and survivors spoke of carnage.

"I saw body parts flying in the air," one fruit trader, Afzal Khan, told the Associated Press. "People were dying. People were crying. People were running."

Police sources at the scene say the bomb contained nuts and bolts, the shrapnel adding to its capacity to kill and maim.

In a statement, the Pakistani Taliban (TTP) said it strongly condemned the attack.

"The killing of innocent people in attacks on public places is regrettable and prohibited by Islam," it said.

Correspondents say the TTP sits at the helm of a loose network of territorially independent militant groups who have different agendas. Not all of them will favour peace talks.

Asked whether he accepted the Taliban denial, the interior minister said it was too early to make a judgement. He said he did not want to make any accusations until the investigations were completed.

Image copyright AFP Image caption The bombing happened during one of the busiest times of day for the wholesale fruit and vegetable market

Image copyright AP Image caption The explosion sent boxes of produce flying

The blast comes a day after 13 people were killed in a bomb attack by separatists in Balochistan province. The long-running insurgency in Balochistan is separate to the Taliban campaign which has raged in Pakistan since 2008.

Except for an attack on a courthouse last month, the Pakistani capital has been relatively peaceful in recent times, our correspondent reports.

Eleven people were killed in the assault on the judicial complex, for which a splinter group of the Pakistani Taliban admitted responsibility.

The casualty toll in the latest attack makes it the deadliest in the capital since the bombing of the Marriott Hotel in 2008, our correspondent adds.

The peace talks with the Taliban were a key campaign pledge for Mr Sharif before he was elected to office for a third time last year.

Thousands of civilians, militants and security personnel have been killed in the Taliban insurgency in Pakistan over the past decade.