ANKARA, Turkey (AP) - Turkish Prime Minister Recep Tayyip Erdogan on Monday again dismissed street protests against his rule as actions organised by extremists, described them as a temporary blip and angrily rejected comparisons with the Arab Spring uprisings.

Appearing defensive and angry on the fourth day of disturbances, he lashed out at reporters who asked whether the government had understood "the message" by protesters airing grievances or whether he would soften his tone.

"What is the message? I want to hear it from you," Erdogan retorted.

"What can a softened tone be like? Can you tell me?" he said. He spoke to reporters before leaving on what was planned to be a four-day trip to Morocco, Algeria and Tunisia.

Turkey has been hit my demonstrations since Friday that grew out of anger over excessive police force against protesters holding a sit-in to prevent the uprooting of trees at Istanbul's main Taksim Square. The demonstrations have since spiralled into Turkey's biggest anti-government disturbances in years, challenging Erdogan's power.

The demonstrators, mostly secular-minded Turks, took to the street airing frustrations at Erdogan's abrasive and non-compromising style as well as the heavy-handed police response to protests. Some of the protesters clashed with police, but most of the protesters demonstrated peacefully. Erdogan has called the protesters "a bunch of looters." Violence flared in Istanbul early on Monday between a group of demonstrators and police on the fourth day. The Dogan news agency said police fired tear gas at the group in an area close to Erdogan's Istanbul office. The protesters responded by hurling stones.

The agency said as many as 500 people were detained overnight on Monday after police broke up protests by several thousands of people in the capital Ankara. Turkey's Fox television reported 300 others detained in a similar crackdown in Izmir, Turkey's third-largest city.