BEIRUT, Lebanon - Syrian President Bashar al-Assad was in Lebanon Friday for the first time since the 2005 murder of ex-premier Rafiq Hariri, in a joint mission with Saudi King Abdullah to defuse a tense political situation.

The two leaders arrived together from Damascus and met Lebanese President Michel Sleiman and other officials to address tensions over reports of an impending indictment against members of the militant party Hezbollah for Hariri's murder.

The discussions were also expected to touch on the overall Middle East situation.

Assad and Sleiman also met separately for about 20 minutes.

It is the first visit to the country by Assad since Hariri's assassination soured bilateral ties and forced the pullout of Syrian troops from Lebanon after a 29-year presence.

Damascus has consistently denied accusations that it had a hand in the killing.

Relations between the two countries have been on the mend since 2008, when diplomatic ties were established for the first time. Prime Minister Saad Hariri, son of the slain Sunni leader, has also made four trips to Syria in the past eight months.

Saudi Arabia, a staunch supporter of the Hariri family, has played a key role in the rapprochement between the Arab neighbours.

Saudi and Syrian flags were on display throughout the Lebanese capital on Friday along with huge portraits of the Saudi monarch.

Security was also tight, with additional army and police deployed.

The visit by the Saudi and Syrian leaders is scheduled to last only three hours and includes a lunch to be attended by some 250 officials, among them members of the unity government which includes two Hezbollah ministers.

"The whole visit is about containing the situation for the immediate future," said Sahar Atrache, a Beirut-based analyst with the International Crisis Group think-tank.

The Arabic-language newspaper An-Nahar, which is close to Hariri's Saudi- and Western-backed governing coalition, called the summit "historic."

"This joint visit is historic and decisive because of its timing and the consequences it can have on a mounting crisis in Lebanon related to the tribunal," it said.

Fears of renewed conflict rose last week after Hezbollah leader Hassan Nasrallah revealed that he knew the UN tribunal probing Hariri's murder was poised to indict members of his party, which is backed by Syria and Iran.

He made it clear that he would not accept such a scenario, accusing the tribunal of being politicised and part of an Israeli plot.

"The Arab leaders' visit to Lebanon is an opportunity to show Arab unity in the face of this plot which aims to destabilise Lebanon and sow sedition," Hezbollah deputy Hassan Fadlallah told AFP.

Analysts say that in addition to threatening civil peace, an indictment of Hezbollah members would deal a blow to the party's reputation and destabilise Hariri's unity government.

The Saudi monarch is expected to press Assad to use his influence over Hezbollah to avoid a political stalemate or a sectarian conflict similar to the one which brought Lebanon close to a new civil war in 2008.

Assad last visited Lebanon in 2002, and King Abdullah is the first Saudi monarch to visit the country since 1957.

Also coming to Beirut later on Friday is the emir of Qatar, Sheikh Hamad bin Khalifa al-Thani. The emir, who is staying until Sunday, is to meet separately with Lebanese leaders and is due to visit the south of the country.