A powerful car bomb exploded in Karachi this morning, killing three people in a KFC restaurant across the road from the hotel where the England cricket team are scheduled to stay next month.

The bomb detonated shortly before 9 o'clock this morning in the city's crowded business district, ripping out windows from nearby buildings and turning over cars. At least 15 people were injured in the blast, six of whom suffered severe burns.

It was unclear whether the KFC outlet, which was closed at the time, was the intended object of the blast. Two branches of the franchise have been attacked in Karachi in recent months but the restaurant, on Dr Ziauddin Ahmed Road, shares its building with several oil companies, which police said could have been the target.

"Indications are that extremist and militant organisations could be involved in the blast," said Salahuddin Haider, a spokesman for the Sindh provincial government in Karachi.

A police explosives expert said the bomb, made of military-style RDX explosive and gunpowder, weighed around 5kg (10lbs), and was detonated by a timing device. CCTV pictures revealed that the bomb was concealed in a small Suzuki sedan.

Police said the three killed were security guards for Muslim Commercial Bank, which also shares the building with KFC and is opposite the Sheraton Hotel where the England cricket team will spend two nights when they play a one-day international match in Karachi on December 15.

The England and Wales Cricket Board said it would consult the Foreign and Commonwealth Office and wait until it had received "a full report on today’s bomb blast in Karachi from its security advisers" before making a comment. The England team declined to comment on the explosion after the fourth day of their Test match in Multan, 1000km (600m) away.

But Shaharyar Khan, chairman of the Pakistan Cricket Board, said there was no need to panic and expressed his hope that the tour would continue.

"We will not take any decision on the Karachi one-dayer in a panic," Mr Khan told reporters. "We hope that the blast will not affect the Karachi one-dayer and the tour... We need to know the motives and the target behind this bombing and will review the situation after two to three days," he said.

"Bomb blasts have been part-and-parcel of life these days and if Australians can play in England despite the London bombings and Sri Lanka can play in India after the Delhi blasts then England can also play," said Mr Khan. "No one likes the terrorists to win."

Pakistan has suffered from the security fears of visiting teams since the September 11 attacks. Since England last toured the country in 2000, Pakistan has hosted 13 home Test matches. England has hosted 35 in the same period.

Karachi, frequently beset by explosions and riots, is a source of particular concern and England refused to play a Test match there. In May 2002, the New Zealand cricket team abandoned its tour of Pakistan after 11 French naval technicians were killed by a suicide bomb at the Sheraton Hotel.

Western fast-food restaurants are a common target for extremist groups in Karachi. A KFC restaurant and a McDonald’s outlet were bombed within minutes of each other in September and in May, six KFC employees were burned to death when their restaurant was torched by a mob during an outbreak of Muslim sectarian violence.

The British High Commission in Pakistan said it would not be altering travel advice for Karachi, which already warns nationals to "avoid western food outlets where possible".