KATHMANDU - Twenty people were killed and 16 others injured after an Indian passenger bus with 43 aboard skidded off the road in central Nepal on Friday, a Nepali official said.

Twelve of the injured have been airlifted to the capital Kathmandu for treatment and four others shall be sent as well in a while, said Janardan Gautam, chief district officer of Tanahun district where the accident happened.

The remaining seven have also been found, but their conditions are yet to be confirmed, he told Xinhua.

"All the 43 passengers have been retrieved, among them 20 have been killed," he said.

The bus fell into the bank of the Marsyangdi river at Tanahun's Aanbookhaireni as a huge stone stopped it from falling further, said Deepak Kumar Raya, spokesperson for the district police.

He told Xinhua that the accident occurred when the bus was heading to Kathmandu from Pokhara, a popular tourist attraction in Nepal.

Driving becomes more difficult and dangerous in mountainous Nepal during the monsoon season.