The blast took place at a wholesale fruit and vegetable market in the busy morning period on Wednesday when grocers and sellers gather to trade.

It is the deadliest attack to hit the Pakistani capital since the Marriott Hotel bombing in 2008 and comes as the government tries to negotiate an end to the Tehreek-e-Taliban Pakistan's seven-year insurgency.

"50 people were also injured in the blast," Pakistan Institute of Medical Sciences (PIMS) spokeswoman Ayesha Isani said.

She said the condition of two patients was very critical.

The blast came a little over a month after a gun and suicide bomb attack on a court complex in Islamabad killed 11 people including a judge.

Pakistan has been in the grip of a bloody homegrown Taliban insurgency since 2007 but there have been very few attacks in recent years in the capital.

BA/BA