At least 15 Indian children have been killed and 45 others injured after a school bus they were travelling in collided with a truck in the northern state of Uttar Pradesh.

The crash happened on Thursday morning in Etah, around 265km (164 miles) from the state's capital, Lucknow.

A senior police officer told the BBC that 14 students "were in a critical condition".

Prime Minister Narendra Modi said he was "anguished by the tragic accident".

Police spokesperson Rahul Srivastava said the exact cause of the accident was yet to be ascertained.

But he added that visibility was poor because of dense fog at the time of the crash.

The victims were aged between three and 12 years and were studying in a local school.

India has the world's highest number of road deaths, with an accident taking place every four minutes.

More than 146,000 people were killed in road accidents in 2015.

Most crashes are blamed on reckless driving, poorly maintained roads and ageing vehicles