Blasts at a multi-storey hotel in the Bangladesh capital Dhaka injured more than 30 people, police said on Monday.

They said two explosions rocked the nine-storey Orchard Plaza hotel at the city's Nayapaltan area late on Sunday night, setting two upper floors on fire.

Firefighters said the victims included one Sri Lankan national. They said the fire was apparently caused by "gas explosions".

The hotel also had guests from Nepal, Singapore and India, witnesses said.

A Nepali hotel guest said the second blast occurred three and half hours after the first one, and it was much bigger.

"It's not a bomb," one fire official told reporters.

The injured were being treated at hospitals for multiple burn injuries.

"We are checking the whole place. Bomb or gas, it's a serious incident and we taking it seriously from security point of view," said a senior police officer on the scene.

Ashish Chokhani, a Nepali citizen, who was in Dhaka for a business trip, said the first blast took place at about 9.15 p.m. (1515 GMT) on the sixth floor of the hotel.

"I ran out of my room and went down, and came back after some time. At around 11.30 there was a bigger blast on the hotel roof and the hotel was immediately vacated by all boarders," he said.

"People were saying the blasts were caused by leakage in gas pipelines on the roof and there was a big fire," Chokhani told Reuters over telephone, on Monday.

In recent years Bangladesh has been repeatedly hit by bomb blasts, mostly blamed on Islamist militants, which have killed dozens of people and injured hundreds.