Most of the passengers were below the age of 10, police said. The bus driver and two teachers were also killed in the accident on Monday evening.

The incident occurred in the northern state of Himachal Pradesh.

Road accidents are common in India, often due to poor driving or badly maintained roads and vehicles.

Monday's accident, which occurred about 325km (200 miles) from the state capital, Shimla, involved a bus transporting some 40 students from Wazir Ram Singh Pathania Memorial school in Nurpur in the country's Kangra district.

"The bus rolled into a 200ft (61m) deep gorge, killing 27 schoolchildren, two teachers and the driver," local police official Santosh Patyal told AFP news agency.

Eyewitnesses said the vehicle skidded as it turned a corner and left the mountainous road, India's ANI news agency reported.

India's National Disaster Relief Force (NDRF) was called to the crash site and is continuing its efforts to reach any passengers trapped in the wreckage.

Prime Minister Narendra Modi's office tweeted that Mr Modi was "anguished" over the news of the deaths.

"My prayers and solidarity with those who lost their near and dear ones in the accident," he is quoted as saying in the tweet.

Authorities in the region have called for an investigation into the incident.