There were reports of confrontations near the Interior Ministry, which oversaw the elections, and in Vanak Square, in north-central Tehran, and the city's text messaging services — a major form of communication here — were not working.

(McClatchy) A reporter saw groups of armored, baton-wielding special forces units charge and disperse groups of students along central Vali Asr Street, occasionally striking civilians with their batons.

(BBC) A crowd of about 3,000 attacked the police, some of whom were on motorbikes, which they set on fire. The sky was thick with black smoke. Police attacked the crowd with sticks and maybe teargas.

I didn't expect to see people turning on the secret police. We were filming when we were surrounded by angry secret policemen. The crowd turned on them and chased them off.

I suspect we are not looking at a revolution but there is serious anger. It all depends on how the government responds - if they use violence, that could inflame the situation.

John Simpson - BBC