A passenger train has derailed in northeastern Iran, killing at least seven people and wounding 12.

Local official Mohammad Reza Kazami said: 'The train was en route from the northeastern city of Mashhad to Tehran.

'So far seven passengers out of 50 aboard have been killed and 12 wounded. The death toll is expected to rise.'

State television has put the death toll at eight and said four people are in a critical condition.