Seven children were killed and 25 people injured when a train ploughed into a packed school bus on a level crossing in the French Alps, local officials said.

The passenger train, linking Evian-les-Bains and Geneva, struck the bus that was carrying 50 pupils and six adults in the village of Mesinges near the town of Allinges.

The 12- to 13-year-olds, from a local school in Margencel, were on a history outing to the medieval village of Yvoire near the Swiss border, according to the local prefecture.

According to the latest toll by the local prefecture, seven children died in the crash, with three people seriously injured and 22 others slightly injured. Several train passengers were among those hurt.

The train and bus drivers were unhurt but "extremely shocked", the local gendarmerie said. Both have been questioned by police.