Turkish police fired tear gas at protesters who marched on Prime Minister Recep Tayyip Erdogan's offices in Istanbul and Ankara on Sunday in a third day of clashes sparked by anger at his Islamist-rooted government.

White fumes filled the air as riot cops fired gas and lashed stone-throwing protestors with water-cannons in the two cities, the latest in a string of nationwide clashes that have left scores injured.

"Dictator, resign!" yelled the crowds in Ankara. "We will resist until we win".

Police had withdrawn on Saturday from Istanbul's main Taksim Square, the symbolic heart of demonstrations that started over an unpopular building project nearby and boiled over into a general protest against the government.

Crowds of whistling, flag-waving protestors continued to cover Taksim Square but the flashpoint shifted late Sunday to Erdogan's nearby Istanbul base, where AFP reporters saw police disperse thousands of demonstrators.