BEIRUT (Reuters) - Two rockets hit a Shi'ite Muslim district of Beirut on Sunday, driving home the risk of spillover from Syria's civil war, after the head of Lebanese Shi'ite militant Hezbollah said it would keep fighting on the Syrian government's side until victory. The United States and Russia have proposed an international peace conference to douse a civil war that has killed more than 80,000 people, driven 1.5 million Syrians as refugees abroad and raised the specter of sectarian bloodshed in the wider region. Syria's government will "in principle" attend the talks tentatively set for June in Geneva and believes it will be an opportunity to resolve the crisis, Syrian Foreign Minister Walid al-Moualem said during a visit to Baghdad on Sunday. But in an apparent rebuff of Western calls for Assad to cede power as part of any deal on a political transition, Moualem said: "No power on earth can decide on the future of Syria. Only the Syrian people have the right to do so. The U.S. and Russian foreign ministers, striving to refloat a plan for a political transition in Syria, were due to meet in Paris on Monday to work out the details. Whether the exiled Syrian civilian opposition will take part in the envisaged peace talks - and be able to negotiate effectively, given their internal divisions and shaky rapport with rebels inside Syria - remains in doubt. The United States has been prodding opponents of Syrian President Bashar al-Assad to unite before the conference. But the Islamist-dominated coalition has been hamstrung by power struggles during talks going on in Istanbul aimed at broadening its representation and electing a cohesive leadership. The talks stalled on Sunday in a factional dispute over proposals to dilute Qatar's influence on rebel forces, with Saudi Arabia angling to play a greater role now that Iranian-backed Hezbollah was openly fighting for Assad. Syria's conflagration has polarized tiny Lebanon, with Sunni Muslims supporting the mainly Sunni insurgency against Assad, and Shi'ite Hezbollah standing by the president, whose minority Alawite sect derives from Shi'ite Islam. In Sunday's attack, one rocket landed in a car sales yard next to a busy road junction in south Beirut's Chiah neighborhood, and the other struck an apartment several hundred meters away, wounding five people, residents said. Brigadier Selim Idris, head of Syria's Western-backed rebel military command, told Al-Arabiya Television that his forces had not carried out the attack. He urged rebels to keep their conflict inside Syria. But another Syrian rebel, Ammar al-Wawi, told Lebanon's LBC Television the attack was a warning to authorities in Beirut to restrain Hezbollah. In coming days we will do more than this. This is a warning to Hezbollah and the Lebanese government to keep Hezbollah's hands off Syria," he said. Hezbollah leader Sayyed Hassan Nasrallah had declared on Saturday night that his heavily armed fighters were committed to the conflict against what he called radical Sunni Islamist rebels in Syria, whatever the cost. French Foreign Minister Laurent Fabius condemned the violent spillover into Lebanon. Until recently, Nasrallah insisted that Hezbollah had not sent guerrillas to fight alongside Assad's forces. Syrian government forces reinforced by Hezbollah launched an onslaught last week on Qusair, a rebel-controlled town close to the Lebanese border that rebels have used as a crucial supply corridor for weapons coming into the country. For Assad, taking Qusair would reconnect Damascus, the capital, with the Alawite heartland on Syria's seacoast and help sever links between the rebel-held north and south of Syria. Lebanese authorities, haunted by Lebanon's own 1975-1990 civil war and torn by the same sectarian rifts as Syria, have pursued a policy of "dissociation" from the Syrian turmoil. But they are unable to stem the flow into Syria of Sunni Muslim gunmen who support the rebels and Hezbollah fighters who back Assad, and have struggled to absorb nearly half a million refugees coming the other way to escape the fighting. At least 25 people have been killed in Tripoli in the north of Lebanon over the last week in Sunni-Alawite street fighting triggered in part by the battle for Qusair across the frontier. In Lebanon's Bekaa Valley, residents said three rockets landed on Sunday close to the mainly Shi'ite border town of Hermel, without causing injuries. Rebels have targeted Hermel from inside Syria several times in recent weeks. Nasrallah's speech was condemned by former prime minister Saad al-Hariri, a Sunni who said that Hezbollah, set up by Iran in the 1980s to fight Israeli occupation forces in south Lebanon, had abandoned anti-Israeli "resistance" in favor of sectarian conflict in Syria. Hariri is backed by Saudi Arabia, which along with other Sunni Muslim Gulf Arab monarchies has strongly supported the uprising against the Iranian-backed Assad. Additional reporting by Khaled Yacoub Oweis in Istanbul, Laila Bassam and Erika Solomon in Beirut, Ahmed Rasheed and Suadad al-Salhy in Baghdad, John Irish in Abu Dhabi; Writing by Mark Heinrich; Editing by Will Waterman