Witnesses say Syrian intelligence agents in the Lebanese capital have begun evacuating their headquarters, one day after a massive protest in Beirut aimed at ending Syria's military presence in the country.

Syrian agents were reported loading equipment onto pickup trucks under the supervision of Lebanese police.

On Monday, hundreds of thousands of protesters in Beirut held the biggest anti-Syria rally since last month's assassination of former prime minister Rafik Hariri. Lebanon's opposition blames Damascus and Beirut's pro-Syrian government for the killing, but both deny involvement.

Meanwhile, Lebanese soldiers and riot police deployed Tuesday outside the U.S. embassy in Beirut, as hundreds of pro-Syrian protesters marched on the U.S. compound and burned an American flag. Demonstrators accused Washington of pressuring Syria to withdraw from their country.

In other developments, Egyptian President Hosni Mubarak paid an unscheduled visit to Damascus today, for talks with Syrian President Bashar al-Assad that diplomats say focused on the Syrian withdrawal.

Some information for this report provided by AP and Reuters.