ISLAMABAD, Oct 28: An American diplomat was among up to seven people wounded in a 'powerful' explosion at the Marriott hotel in Islamabad on Thursday night, US officials, police and witnesses said.

Hotel employees said the explosion occurred at around 9.35pm at the entrance of the hotel, and that they believed it was the result of a bomb.

Authorities insisted, though, the most likely cause was an electrical short-circuit and that there was no initial evidence that pointed to a terrorist attack.

"It was evidently a case of short-circuiting," Interior Minister Aftab Sherpao told reporters at the scene.

"The forensic people have come and we are checking the whole place but there's no evidence so far of any terrorist activity or any blast in that sense."

A US State Department official in Washington said 11 staffers from the US embassy in Islamabad were having an evening meal at the Marriott when the explosion occurred.

The official said one of the diplomats suffered minor injuries and the others were unhurt.

DSP Islamabad Khalid Masood told reporters that at least seven people were injured, "three or four" of whom were foreigners.

He said a Pakistani employee of the hotel was in a critical condition with burns to 90 per cent of his body.

The explosion shattered the glass entrance of the hotel, with the X-ray machine used to screen people as they entered almost completely destroyed.

"It seems to be a bomb explosion. The bomb was apparently hidden in one of the flower pots near the entrance of the hotel," hotel employee Khurram Ahmed told AFP at the scene.

"The blast was huge. It shook everyone in the hotel." When told hotel employees said they believed the blast was caused by a bomb, Information Minister Shaikh Rasheed told AFP: "That's not true. It was an electrical short-circuit."

Hotel security guard Mohammad Salem said he heard a powerful explosion. "Broken glasses flew around us. I felt a shock and fell down. There was blood on the floor around me. We don't know what was the source of the blast but it was a very powerful blast."

Hotel guests in their rooms well away from the entrance said they felt the explosion.

"I was in my room and I thought there was some earthquake, I rushed out of the hotel," guest Mohsin Ahmed said.

"There was panic and people were trying to get out of the premises."

The usually glittering lobby was also badly damaged with glass shards and broken chandeliers scattered on the ground.

The hotel is located in the heavily guarded area close to official residences of federal ministers and provincial legislatures.

Talking to newsmen after visiting the spot, Interior Minister Aftab Sherpao said there was no evidence of any terrorist activity in the explosion.

Apparently the explosion was the result of short circuiting in the lobby of the hotel, he said.

The minister said Wapda officials had been summoned to investigate and determine the real cause of the blast.

The injured persons suffered minor injuries, Mr Sherpao said. Among them, three are hotel employees.

Police and local administration officials rushed to the scene and cordoned off the entire area. -AFP/APP