At least eight people have been killed and up to 22 injured in a bomb explosion in the Pakistani city of Karachi.

Eyewitnesses say there was a huge explosion as the bomb went off on Arambagh road in the centre of the city at 1900 local time (1400 GMT).

Reports say the explosive appeared to have been hidden in a fruit cart.

Windows in nearby buildings were smashed in the blast and the bomb left a huge crater on the road.

"I was just crossing the road to buy myself a pack of cigarettes when there was a massive blast," said Akbar Ali, a shopkeeper.

"I turned around and only saw smoke and heard screams and shouts. It was like an earthquake," he said.

Most of the injured were moved to hospital and police cordoned off the area.

"It was a powerful bomb," the AFP news agency quoted bomb disposal squad chief Moeen Uddin as saying. "It was probably home-made and most probably connected with a timer," he said.

The BBC's Owen Bennett-Jones, who is in Karachi, says such attacks in public places have been taking place all across Pakistan.

No one comes forward to claim responsibility for them and they often remain unresolved.

But the governor of Sindh province, Mohamed Azim Daud Pota, has accused the Indian intelligence agency, Raw (Research and Analysis Wing), of being behind this latest attack.

"It has to be a foreign hand, no Pakistanis can do it," he said while visiting the injured in hospital.

Arrest

On Sunday, police in the Pakistani capital, Islamabad, arrested a member of the Indian High Commission and accused him of carrying explosives.

They said the high commission staff member, P Moses, confessed that he was carrying the material to be delivered to someone who said he would leave it in a marketplace in Rawalpindi.

India has reacted strongly to the allegation and rejected any suggestion that Mr Moses was carrying any explosives.

Karachi, which is in the southern province of Sindh, has been plagued by sectarian violence for several years.

More than 4,000 people have died in violence in the past four years.

Last year, then premier Nawaz Sharif placed Sindh under direct federal rule, in an effort to curb the growing level of violence.