Police in India are said to be investigating an attack on a bus carrying 70 Christians home from a national conference for believers earlier this month.

The group had been attending the Third National Congress of the Synod of Pentecostal Churches in Tamil Nadu.

Three men on motorcycles verbally threatened passengers before smashing the windscreen of the bus, causing injury to the driver and passengers which included children and the elderly.

Police arrived on the scene within 15 minutes and have registered a First Information Report, which means an investigation can now take place.

It's thought religious extremists who were aware of the gathering of Christians were behind the attack.

Religious freedom charity Christian Solidarity Worldwide is calling on police to hold those responsible to account.

Chief executive Mervyn Thomas said: "This attack on a group of Christians returning from a national gathering is a worrying example of the religious intolerance and violence that is being allowed to fester and take root in the largest democracy in the world. 

"Religious minorities in India should feel safe and free to practice and profess their religion or belief without any fear of reproach, and we call on the authorities to put an end to all forms of institutional propaganda that incite hate towards religious minorities. 

"The police must follow up with a thorough investigation of this incident and not allow themselves to be influenced by hardline religious nationalists as they seek to hold those responsible to account."

The National Congress had previously seen leaders call on Christians to pray for peace in India at a time where believers are increasingly being targeted, with churches closed, prayer meetings disrupted and individuals targeted.