Buses and cars were left stranded when roads across London flooded on Sunday, as repeated thunderstorms battered the British capital.

Emergency services were battling "significant flooding across London", Mayor Sadiq Khan tweeted, adding that all public transport services were affected and advising people to avoid walking or driving through flooded areas.

Social media users posted videos of partially submerged vehicles in southwest London, with more heavy rain set to fall as a band of thunderstorms made its way across southeast England.

The Met Office issued an amber weather warning across London and surrounding counties until 7 pm local time (1800 GMT).

It warned there was a risk of lightning strikes and flooding, with up to 10 centimetres (four inches) of rain forecast to fall in some areas, almost double the monthly average for July.

The Met Office issued an amber weather warning and said there was a risk of lightning strikes and flooding
Flash Flood | Representational Image AFP / JUSTIN TALLIS

Police closed a road near Queenstown Road station in southwest London, where three double-decker London buses were stuck under a railway bridge, according to an AFP journalist.

A driver, who gave his name as Eric, said passengers had to get off after his bus started taking on water.

Other motorists in Walthamstow, northeast London, abandoned their vehicles as the rain hammered down.

Police said they were "currently dealing with numerous floods in the east," warning that tunnels and roundabouts were submerged.