Italian police on Wednesday, March 20 rescued 51 children taken hostage by their school bus driver, who doused the vehicle in petrol and set it alight apparently in protest at migrant deaths in the Mediterranean, The Standard reports.

Some of the children were tied up during the 30-minute ordeal, which saw the bus slam into a car but was brought to an end by police after one of the children was able to call for help. No one was seriously injured.

"It is a miracle, it could have been carnage. The police were outstanding, blocking the bus and getting the children off," said Milan prosecutor Francesco Greco.

Photos showed the burnt-out shell of the bus and the car, which were travelling on a road near Milan.

Driver Ousseynou Sy -- a 47-year-old Italian citizen of Senegalese origin -- explained under questioning that he wanted "to draw attention to the consequences of migration policies", according to his lawyer.

The 51 students in year two of secondary school in Crema were coming back from a sports outing accompanied by three adults when the driver abruptly changed route, announcing he was taking them all hostage.

"No one is getting out of here alive," he said, according to several of the students.

A dozen children and two of the adults were taken to hospital for smoke inhalation while the arrested driver also needed treatment for burns to his hands.

The Milan police anti-terrorism unit has been charged with investigating the hostage-taking which lasted a little over 30 minutes.