CAIRO (Reuters) - Egyptian police detained one protester and scuffled with others among a group of about 200 demonstrating on Tuesday for an end to President Hosni Mubarak's 29-year rule, a security source and witnesses said.

The protest was organised by Egypt's two most active grassroots groups, the Sixth of April Youth and Kefaya (Enough), which want changes to the constitution to free up politics and an end to emergency law that allows indefinite detentions.

Egypt holds a parliament election later this year and a presidential vote next year. The president's ruling party is expected, as usual, to dominate in the assembly. Rights groups have cited widespread abuses in past votes.

Mubarak, 81, had gallbladder surgery in Germany in March and has not been seen in public since returning last month. He has not said if he will run for another term.

The protesters were surrounded by police in riot gear and scuffles started when some demonstrators tried to break through a cordon to start a march from a court complex in central Cairo, Reuters witnesses said.

Protesters chanted "Down, down, Hosni Mubarak" and other anti-government slogans.

Reuters Television images showed police hitting several protesters.

"The police were rough with us and attacked and detained one of us ... We tried to get away from the police surrounding us, but they did not let us," Fawzy, a protester who gave only his first name, told Reuters.

A security source confirmed one protester had been detained.

The protest followed a police crackdown on a demonstration for political reform in Cairo on April 6, in which 93 protesters were detained, most were freed the same day and the rest later.

Egypt's ally, the United States, said after that protest that it was "deeply concerned" about the arrests. Egypt, one the largest recipients of U.S. aid, dismissed criticism as interference in its internal affairs.

Such demonstrations are rare. Protests briefly gained momentum around the 2005 presidential election, Egypt's first multi-candidate race, at a time when Washington was pushing for democratic change in the region.

But protests rarely numbered more than a few hundred people and police cracked down as U.S. pressure to change eased.