Cairo, Jan 26 (IANS/AKI) Egyptian president Hosni Mubarak's son who is considered as his successor has fled to Britain along with his family, US-based Arabic website Akhbar al-Arab reported.

The plane with Gamal Mubarak, his wife and daughter on board left for London Tuesday from an airport in western Cairo, the website said.

The report came as violent unrest broke out in Cairo and other Egyptian cities and hundreds of thousands of people reportedly took to the streets in a Tunisia-inspired day of revolt.

The protesters want Egyptian government to end its 30-year state of emergency and pass a law preventing a president from serving more than two terms, and want the interior minister Habib al-Adly, to resign.

Protests in Egypt broke out after opposition groups waged an internet campaign inspired by the Tunisian uprising. Weeks of unrest in Tunisia eventually toppled president Zine al-Abidine Ben Ali earlier this month.

A police officer was killed in clashes Tuesday in central Cairo, Egyptian daily al-Wafd reported.

Over 30,000 protesters gathered in Cairo's Maidan al-Tahrir square to take part in the "day of anger", the spokesman for Egypt's '6 April' opposition movement, Mohammed Adel, said.

"Police used tear gas and water canon to break up our protest and they arrested 40 of us, but we don't have official figures on the numbers of arrests across Egypt," said Adel.

Supporters of the '6 April' movement, the opposition al-Ghad party, the outlawed Muslim Brotherhood, the al-Wafd party and supporters of former UN nuclear watchdog chief Mohammed El Baradei took part in the protest.

Al-Wafd daily said police arrested 600 people during Tuesday's protests in Cairo, Alexandria, Port Said, Tantan, al-Mahala, Asiut, al-Bahira and al-Quium. More than 200,000 people took part in protests in these cities.

US secretary of state Hillary Clinton said Tuesday Washington believed the Egyptian government was stable and urged restraint on both sides.