A car is half submerged in a flooded road in Beijing on July 21, 2012. [Photo/Asianewsphoto]

BEIJING - Torrential rains that lashed Beijing Saturday have left at least three people dead and six others injured, local authorities said.

Two people were killed and six others injured as strong winds toppled rooftops in two villages in the city's suburban Tongzhou district, the Beijing Emergency Medical Center said.

The third person, also in Tongzhou, was killed after being struck by lightning.

Also rescuers have reached the 104 primary school students and nine teachers trapped at a military training site in Fangshan district by a flash flood.

The students and teachers were in no immediate danger and the rescuers have brought them hot water and food. The rescue operation was ongoing.

The largest rain this year that started thrashing the city around 10 a.m. Saturday has cut off traffic on some roads inundated by waters and also severely disrupted air traffic.

Authorities have sent out 7,000 traffic police to the city's roads to help cope with traffic problems.

Many roads under overpasses were submerged by waters of up to one meter deep, leaving some cars stranded. Many people therefore chose to take subway rather than drive their own cars.

About 243 flights have been canceled and 272 others delayed by 6:30 p.m., according to the Beijing Capital International Airport.

The metro line linking the airport with the downtown area resumed operation at 10:05 p.m. after two and a half hours' suspension due to rain-triggered power failure.

The line's service will be extended by one hour to midnight to carry stranded passengers, the metro line's operator said in a statement. Also free shuttle bus service is offered.

Beijing received 117 mm of precipitation on average as of 8 p.m., with a township in the suburban Mentougou district hit by the largest of 345 mm, according to the Beijing Meteorological Bureau.

The agency issued its first orange rainstorm alert warning since 2005 Saturday evening as the rain is forecast to last over 20 hours till Sunday morning.

Chinese meteorological authorities use a four-tier color-coded weather warning system from "blue", "yellow" to "orange" and "red".