Lebanon’s state news agency says a rocket has been fired from the south of the country towards Israel.
There is no news on who may be responsible, or of any damage or casualties.
It comes after two rockets hit a Hezbollah area of southern Beirut. Four people were injured.
The Israeli military says people in the northern town of Metula claim to have heard an explosion.
A few days ago, Hezbollah leader Hassan Nasrallah confirmed the group’s involvement in Syria’s conflict.
The news is likely to stoke fears of a regional escalation.
There have also been clashes between pro-and anti-Assad fighters in Tripoli.
Thirty-one people, including six soldiers, have died there in six days.
In Baghdad, meanwhile, Syria’s Foreign Minister says he has agreed “in principle” to take part in international peace talks in Geneva next month.
Wallid al-Moallem says his government believes the conference, proposed by Russia and the United States, is a good opportunity for a political solution to the crisis in Syria.
And in Istanbul, dozens of Syrians gathered outside an hotel where the country’s opposition are meeting to discuss strategy.
For the demonstrators, tackling the ongoing conflict is more important than political positioning.