Scores of people had to be evacuated from their homes by firefighters on Thursday night after what was thought to be sewage flooded streets in south London.

Water from a burst main in Kennington mixed with silt and mud, sending pungent floodwater on to the surrounding streets and into homes, witnesses said.

"It's not clear how they are going to stop it. The water is revolting, brown, muddy – well I hope it's mud," said one resident, Angela Reynolds, 58. She added: "The road has been made into a river. It's a bit like Somerset. There are lots of basements around here. One of the houses has already been badly flooded. The water just flooded the road in 10 minutes. It was quite incredible."

Firefighters were pictured carrying people to safety by local resident Lewis Whyld. "People now getting trapped by sewage in south London, firefighters evacuating properties."

In another Twitter post, he added: "Expect lower ground floor flats to be full of sewage in south London tonight, it's getting deeper too."

Marcus Eyskens, 24, who was among the onlookers in Clapham Road, said: "It's blocked all the road. It's a lot of water. It'll probably take a few days to get it under control."

Clapham Road, one of the area's major arteries, was closed by emergency services. The London Fire Brigade said that five other roads in the area were affected by waters that had risen to "100 millimetres" by around 10pm on Thursday.

A spokesman said: "We received a call reporting flooding in the area. Four fire engines are on the scene and Thames Water are on the way to try and fix the problem. It is very much an ongoing incident."

A Metropolitan police spokesman said: "There is flooding on Clapham Road between Oval and Stockwell stations, which has been caused by a suspected burst water pipe. We are asking people to avoid the area."

Several fire engines, police cars and an ambulance attended the scene near Oval Tube station, while a London Underground Emergency Response Unit were also deployed.

A Transport for London spokesman said part of Clapham Road was closed but the Tube was not affected. A spokeswoman for Thames Water said: "A burst water main has caused flooding to Clapham Road. Engineers are on site working to manage the burst."