Lebanon is marking the first anniversary of former premier Rafiq Hariri's assassination in an emotional commemoration as the country struggles to unite in the shadow of its former powerbroker Syria.

Hariri's son Saad returned home at the weekend after six months in exile to issue an emotional appeal for a massive turnout as a show of Lebanese reconciliation.

"It will be a day of a renewal of faith in the unity of Lebanon," said Hariri, now the head of the anti-Syrian majority in parliament.

"I call on all Lebanese to adopt a historic position of unity on this day to show that our national unity is above all else and that the forces of March 14 will remain united."

Candlelit rallies and concerts are planned to mark the massive Beirut seafront bombing that killed Hariri and 20 other people plunging Lebanon into shock and political turmoil.

Almost one million people of all Lebanese religious groups, or a quarter of the population, turned out last March 14 for a demonstration of grief and anti-Syrian protests one month after the assassination.

Syria, which pulled out its troops from Lebanon after a three-decade military presence, has been implicated in the Hariri murder by a UN commission of inquiry and several top officials have been interrogated.

"We do not ask for a change of regime in Syria, but that it makes peace. We thank Syria for having ended the war in Lebanon but we will handle our own affairs now," Saad Hariri said in an interview with Lebanese television.

"The Syrian regime did a lot wrong in Lebanon and spared her neither insults nor threats."

Saad Hariri has lived in France and Syria in fear of his life after a wave of attacks against prominent anti-Syrian politicians and journalists, some of them deadly, in the wake of the Hariri slaying.

The United States, which has been leading the campaign against Syria, said said Monday that those responsible for the assassination will be brought to justice.

"The international community will not rest until we get to the bottom of who is responsible and see that those responsible are held to account for what they have done," State Department spokesman Sean McCormack told reporters.

"So it will take a while. It has taken a while. But no matter how long it takes, we're going to support the (UN) commission in its work to see that the Lebanese people have a full understanding of exactly what happened on that day and why it happened and find out who is responsible for it," McCormack said.

He said Washington stands "shoulder to shoulder" with the Lebanese people in the bid to see justice is served.

However, in a sign of continuing divisions in Lebanon, the pro-Syrian Shiite movement Hezbollah and a key Christian leader, General Michel Aoun, have refused to endorse the commemoration charging that it had been "politicised".

Hariri was buried in a mosque that he built in central Beirut's Martyrs' Square, popularly renamed Freedom Square after his death.

Beirut has been adorned with billboards in honor of Hariri, a five-time billionaire premier who played a major role in the reconstruction of Beirut after the 1975-1990 civil war. "We miss you," one of them reads.

Restaurants and hotels in Beirut marked Valentine's Day three days early this year so as not to clash with the Hariri commemoration. Florists reported a rush on roses both for lovers and to be placed on Hariri's tomb.

"Every Lebanese is invited to pay homage to Rafiq Hariri on Tuesday by placing a rose at the site of the attack or at his tomb," said Druze leader Walid Jumblatt, an anti-Syrian MP.

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