A series of gas explosions in the southern Taiwanese city of Kaohsiung has killed 20 people and injured about 270, officials say.

The exact cause of the gas leaks is not clear, but reports say the blasts were caused by ruptured pipelines.

Images from the scene show major fires, cars overturned and significant damage to roads and buildings.

Dozens of those injured by the blasts were taken to hospitals for treatment, Taiwan's fire agency said.

"The local fire department received calls of gas leaks late Thursday and then there was a series of blasts around midnight affecting an area of two to three sq km [one sq mile]," the National Fire Agency added in a statement.

'A huge cave'

"I saw lots of cars and motorcycles with engines all over on the road, and doctors checking if bodies were dead or alive, "eyewitness Chen Guan-yuan, who was at the scene shortly after the blast, told the BBC.

"Because the explosion range is so far so it's really difficult to handle this situation immediately," Mr Chen said, adding that the blasts "caused a long range hole, like a huge cave".

Five firefighters are said to be among the dead.

People in the nearby area have been evacuated to schools, local officials say.

Despite firefighting efforts, fires were still out of control in two streets at 05:00 local time (21:00 GMT), five hours after the blasts, local mediareported.

Firefighters are still trying to see if people are trapped under the rubble of the explosion, the BBC's Cindy Sui in Taipei reports.

Taiwan has a late night culture, so there would have been people out and about on the streets at midnight when the blast happened, our correspondent adds.

The multiple explosions were sparked by gas leaks in the sewage system of Kaohsiung's Cianjhen District, Premier Jiang Yi-huah said,according to Taiwanese news agency CNA.

Hundreds of soldiers, and firefighters from neighbouring Tainan City and Pingtung County, had been deployed to assist rescue efforts, Mr Jiang added.