Tens of thousands of Lebanese gathered together in a Beirut city square Wednesday to mark the second anniversary of the assassination of former prime minister Rafik Hariri.

The anniversary came as the government deployed hundreds of troops in response to bus bombings on Tuesday that left three people dead.

Troops wearing full combat gear and armoured military vehicles were deployed in Martyrs' Square where government supporters commemorated Hariri's death, while opposition supporters continued their sit-in protest to demand the government's resignation.

In an attempt to maintain the calm, the troops set up a razor wire barrier to keep the two groups apart, and searched people for weapons.

Prime Minister Fuad Saniora, a longtime confidant of Hariri, prayed at his grave which is located near the square.

Hariri's sister Bahiya, a lawmaker, also said prayers at his graveside.

By late morning local time, the Martyrs' Square was packed with people waving national and political party flags, and balloons printed with pictures of Hariri.

One day earlier, bombs ripped through two buses in a Christian area of Lebanon, killing at least three people.

At least 20 people were wounded in the co-coordinated attack, the state-run news agency said.

The attack occurred shortly after 9 a.m. on a road in the village of Ein Alaq, just south of the mainly Christian town of Bikfaya in the hills northeast of Beirut.

A security official, speaking on condition of anonymity because he was not authorized to talk to media, said the blasts were minutes apart.

As people scrambled to the scene of the first blast, a second explosion tore through a bus that had been following behind, the official said.

The death toll was initially reported as much higher. But the lower toll of three dead brought the count in line with that of the Red Cross.

The Voice Of Lebanon radio station said the targeted buses had been transporting people to work.

Ein Alaq is near Bikfaya, the ancestral home of the Gemayel family, one of the most prominent political Christian families in Lebanese politics.

Cabinet member Pierre Gemayel, a leading anti-Syrian politician, was assassinated in November. His father, former President Amin Gemayel, visited the White House and met with Bush last week.

Walid Jumblatt, a senior pro-government politician, speculated that the blasts were meant to scare people from congregating at the rally to commemorate Hariri, the subject of a UN probe that has pointed the finger of blame at Syria.

"It's to terrorize people who are willing to come," Jumblatt told Al-Jazeera television.

Sectarian tensions have been running high in the deeply divided country.

Lebanon has witnessed 15 attacks on politicians, journalists and public places since Hariri's slaying on February 14, 2005.

Many Lebanese blame the attacks on Syria, which has always denied accusations of involvement. Syria has so far not responded to Tuesday's events.

Lebanon has been locked for months in a power struggle with Hezbollah-led opposition.

The crisis gained momentum when six ministers from Hezbollah and its pro-Syrian allies left their government posts in November mainly over the cabinet's endorsement of a UN tribunal for Hariri's murder.

The anniversary of Hariri's assassination also falls six months to the day that a UN-brokered ceasefire brought an end to a war between Israel and Hezbollah. The summer war lasted for 34 days and left more than 1,000 people dead, with heavy casualties on both sides.

With files from The Associated Press