Two rockets hit Hezbollah district of Beirut
At least three people have been wounded by a rocket strike on the southern part of the Lebanese capital Beirut.
Two rockets hit a district controlled by the Hezbollah organisation, officials and residents were quoted as saying by news agencies.
Tension has been high over the conflict in neighbouring Syria.
On Saturday, Hezbollah leader Hassan Nasrallah promised his supporters they would prevail in Syria, where they are backing President Bashar al-Assad.
Syria on Sunday said it had agreed "in principle" to take part in next month's talks in Geneva aimed at negotiating an end to more than two years of violence in the country.
'Terrorists and vandals'
There was no immediate indication who had fired the rockets in Beirut but Lebanese Interior Minister Marwan Charbel said the projectiles, believed to be 107mm rockets with an 8-km (5-mile) range, had been fired from a position to the south-east.
One security official told Associated Press that rocket launchers had been found in woods in a predominantly Christian and Druse area, although this has not been independently confirmed.
Dozens of militants from Hezbollah, a Shia Muslim organisation, are said to have been killed in recent fighting alongside Syrian troops, who face a mainly Sunni Muslim opposition.
The fiery speech by the Hezbollah leader had raised fears that the involvement of his fighters in Syria would have repercussions in Lebanon, the BBC's Jim Muir reports from Beirut.
The leader of Lebanon's mainly Sunni March 14th movement, former Prime Minister Saad al-Hariri, said that what Hezbollah was doing in Syria was "political and military suicide", our correspondent notes.
The missiles were Grad rockets, a Soviet-made weapon, an unnamed Lebanese security source told AFP news agency. Both landed in the al-Shayyah area.
One struck a car showroom, causing injuries and damaging vehicles. Reports suggest those injured were all Syrian workers.
The second rocket hit a residential building.
A Reuters news agency photo showed the face of a building pockmarked by what appeared to be shrapnel, while video showed shattered windows blown across a living-room.
Another photo showed dazed men with cuts to their legs being treated in the street by friends.
President Michel Suleiman condemned the attackers as "terrorists and vandals".
Syrian rebel commanders have threatened to retaliate against Hezbollah in Lebanon, our correspondent says.
AP reports that an opposition commander in Syria pledged to attack Hezbollah in Beirut.
"We used to say before, 'We are coming Bashar'," Col Abdul-Jabbar al-Aqidi was quoted as saying. "Now we say, 'We are coming Bashar and we are coming Hassan Nasrallah'."
Syrian Foreign Minister Walid Muallem said on Sunday that President Assad's government believed the forthcoming Geneva conference was "a good opportunity for a political solution to the crisis in Syria".
Syria's main opposition group, the Syrian National Coalition, has been meeting in Istanbul for a fourth day to try to come up with a unified stance on the conference.
It has previously said it will attend only if Mr Assad steps down.
Mr Assad is fighting to end a revolt against his rule which began just over two years ago and has left at least 80,000 people dead and made refugees of some 1.5 million.
The Syrian conflict has heightened Lebanon's own sectarian divisions, at times spilling into open conflict.
Fighting in Lebanon's northern town of Tripoli between factions supporting the opposing sides in Syria has left at least 25 people dead in the past week.
Inside Syria itself, opposition activists said many Hezbollah militants were killed on Saturday during fighting for the western town of Qusair, just across the border from Lebanon.
One source close to Hezbollah told AFP that 22 of its fighters had died on Saturday.
A Syrian army source told the agency that fighting was now taking place at the rebel-held Dabaa military airport, north of Qusair.