At least 18 people are now thought to have died following Storm Harvey in Texas.

More than 4,300 people in Houston alone have been rescued by the US Coast Guard since Sunday.

The heaviest tropical downpour in US history has left an area 15 times the size of Manhattan under water, according to the Houston Chronicle newspaper.

A curfew was also introduced by Houston's mayor, amid reports of looting, armed robberies and people impersonating police officers.

With the flooding now entering its fourth day, floods are forecast to worsen over the next 48 hours.

Flood level are set to peak on Wednesday and Thursday, with 51 cm (20in) of rain forecast to fall by the end of the week and up to 127cm (50 in) predicted in some isolated storms.

Damage is expected to run into tens of billions of dollars, making it one of America's most expensive natural disasters.