Clinton tours Tahir Square

US Secretary of State Hillary Clinton has toured Cairo's Tahrir Square, the centre of the popular uprising which toppled Egypt's long-time autocratic leader last month.

Mrs Clinton made an unscheduled stop at the site during a two-day visit to Egypt aimed at encouraging the Egyptian people and their transitional leaders to hold true to the ideals of democratic reforms that propelled the revolution.

She is the highest-ranking US official to visit Egypt since President Hosni Mubarak was ousted last month and she has pledged America's support for the transition.

She was due to meet Egypt's army chief and prime minister before heading to Tunisia, taking the same message.

The success of Tunisia's anti-government protests in January fuelled similar revolts across the Arab world.