Anti-government protests have broken out in Egypt after an internet campaign inspired by the uprising in Tunisia.

Thousands of protesters are marching through Cairo chanting anti-government slogans, after activists called for a "day of revolt" in a web message.

Riot police have tackled protesters in the capital, using tear gas to try to disperse them.

The BBC's Jon Leyne has been watching events unfold and described "remarkable scenes" in the Egyptian capital.