Lebanese militant group Hezbollah has struck an Israeli armoured patrol with a roadside bomb at its border.
The group says it is in retaliation for the killing of one of its high-profile operatives.
Hezbollah said it set off a large explosive device as the patrol passed in the disputed Chebaa Farms area, destroying a vehicle and causing casualties among the soldiers inside.
The Israeli army said vehicles in the area were hit with an improvised explosive device and that it responded with targeted artillery fire. It did not say whether there were any casualties. Hezbollah's television channel Al Manar said one of the vehicles targeted was carrying "a senior officer".
Tensions on the border have been high since Samir Kantar, a celebrated militant who carried out a notorious attack in Israel and spent nearly 30 years in an Israeli jail, was killed in Syria by an air strike late last month. Hezbollah blamed Israel for the strike and said it would avenge his death.
Border skirmishes between Israel and Hezbollah have quickly escalated into all-out war in the past, with one cross-border raid by the group in 2006 starting a month-long Israeli offensive that included a ground invasion and air strikes that reached across all of Lebanon.
But with Hezbollah currently engaged in the Syrian civil war backing President Bashar Assad, and Israel free to target the group in porous Syrian airspace, both sides seem too occupied elsewhere to opt for a new war in Lebanon.
Later, Lebanese security officials said that more than 50 Israeli shells hit several villages in the area where the Hezbollah operation was carried out. Residents along the border said shelling from Israeli tanks and artillery landed in agricultural areas inside Lebanon, but did not report casualties.
The officials said the patrol was hit near an Israeli army position in the Kfar Chouba hills that Lebanon says is Lebanese land occupied by Israel. The residents requested anonymity, saying they feared for their safety, while the officials did so in line with regulations.
The Hezbollah unit that carried out the bombing was named after Kantar, who joined Hezbollah after being released by Israel in 2008. Kantar was killed last month in Syria in an attack blamed on Israel.
Just a day earlier, Hezbollah leader Hassan Nasrallah vowed to avenge the killing of Kantar, who was the longest serving Lebanese prisoner in Israel before he was released in exchange for the bodies of two Israeli soldiers killed in the raid that kicked off the 2006 war.
Kantar was killed on December 19, along with eight others, in an air strike on a residential building in Jaramana, near the Syrian capital of Damascus.
Israel has not confirmed or denied that it carried out the air strikes.