BEIRUT, Lebanon – Tens of thousands marched yesterday in the biggest anti-Syrian protest in Lebanese history amid signals that Syria will soon withdraw its troops from parts of the country. President Bush renewed demands for Syrian forces to leave Lebanon immediately.

The protest marked one week since the February 14 death of Rafik Hariri and began at the bomb-scarred site of the former prime minister’s assassination, which turned many Lebanese against Syria and increased international pressure on Damascus to extract its army from Lebanon.

Holding aloft red roses and Lebanese flags, the throngs on the streets shouted insults at Syria and demanded the resignation of the pro-Syrian government in a march that began at the seaside site where Hariri and 16 others were killed and ended at his grave in the city center.

The protesters wore scarves of red and white – the colors of Lebanon’s flag – which have become the symbol of the opposition’s “independence uprising,” described as a peaceful campaign to dislodge the government and force the Syrian army out of Lebanon.

Hariri’s assassination has brought Lebanese together and strengthened the opposition, but it was unclear if the momentum would force a change in government or push the Syrian army out of the country.

General Michel Aoun, another former prime minister, said yesterday he would return from exile before this year’s parliamentary elections and that he may launch his own candidacy if the opposition needs his support. The former commander of the Lebanese army fled the country in 1990.

“I will return before the legislative elections, probably by mid-April,” General Aoun told the Associated Press in a telephone interview from Paris. “And if the situation is critical for the opposition in a region, then I will throw in my personal weight and run in the elections.”

As the demonstration was under way in Beirut, Mr. Bush issued a strong warning to Syria from Brussels, saying Damascus “must end its occupation of Lebanon.”

In Damascus, Arab League Secretary-General Amr Moussa said Syrian President Bashar Al-Assad affirmed during a meeting that his country will “soon” take steps to withdraw its army from Lebanese areas in line with a 1989 agreement. It was not clear whether that meant Syria would completely leave Lebanon.

Syria, which sent its army into Lebanon in 1976 amid the bloody civil war, has always pledged to implement the 1989 accord that ended the conflict, and has redeployed troops several times since 2000. However, a withdrawal to the eastern Bekaa Valley near the border that was scheduled for the early 1990s, followed by an eventual total pullout, has never been carried out.

Syrian troops here once numbered 35,000; the current number is 15,000, and Syria remains the chief power broker in Lebanon. Syrian Foreign Minister Farouk Al-Sharaa said recently he expects Syrian troops to stay for two more years.

Demonstrators in Beirut beat drums and held up portraits of leaders assassinated during the 1975-90 civil war as they sang patriotic songs. Shouts of “Syria out!” and “Syria is the criminal” competed with loud insults directed against the Syrian dictator – words that until recently few dared to say in public.

Marching past policemen and army troops in full battle gear, some carried banners reading “Independence” and chanted, “The government of puppets must fall” and “Enough blood, leave us alone.” Playing on words, one placard read in English: “Syrial killers.”

In a show of Muslim-Christian unity, some protesters held a copy of the Koran in one hand and a cross in another.

“Enough bloodshed and disasters. It is the 21st century, and people should be able to govern themselves,” said Youssef Mukhtar, a 47-year-old Lebanese-American engineer. “The situation has become unbearable and we have to regain our country.”