Tens of thousands of Georgian opposition supporters have taken to the streets of the capital, Tbilisi, pressing for the resignation of President Mikheil Saakashvili.

Former close allies of the president addressed a large rally near Georgia's parliament Thursday as protesters rallied in the capital and in other cities.

The protesters said they are giving Mr. Saakashvili 24 hours to respond to their demands before announcing further action.

Georgia's former U.N. ambassador, Irakli Alasania, called the rally a demonstration of unity in demanding change through peaceful means.

Former parliament speaker Nino Burdjanadze apologized to the crowd for supporting the president after police used rubber bullets to break up a 2007 opposition rally.

Opposition leaders accuse Mr. Saakashvili of being authoritarian and of leading the country into a disastrous war with Russia last year.

Earlier, Mr. Saakashvili joined some opposition leaders outside parliament for a brief memorial service honoring victims of a deadly Soviet military crackdown 20 years ago  Hundreds of people took part in the brief vigil to commemorate the 20 civilians killed by Soviet troops.

Two years later, on April 9, 1991, Georgia declared independence from the Soviet Union following a nationwide referendum.

Georgian opposition members accused police of detaining supporters and blocking roads in an attempt to prevent people from attending Thursday's rally.  Police denied the claims.

Georgian Interior Minister Vano Merabishvili said police would not interfere with the protest unless lives were threatened, or if attempts were made to take over a government building.

The U.S. State Department Wednesday urged all sides to avoid violence, calling peaceful protests an important part of a democracy.

Some information for this report was provided by Reuters.