Lebanese Prime Minister Hassan Diab said on Tuesday Israel had violated his country's sovereignty with a "dangerous military escalation" along the Israeli-Lebanese frontier on Monday and called for caution after a rise in border tensions.
Prime Minister Benjamin Netanyahu said Israeli forces had thwarted an attempt by the Iran-backed Lebanese Shi'ite group Hezbollah to infiltrate across the Lebanese frontier on Monday. The Iranian-backed Shi'ite group denied this.
A witness in Lebanon counted dozens of Israeli shells hitting the disputed Shebaa Farms area.
"I call for caution in the coming days because I fear the situation will deteriorate in light of heightened tensions on our border," Diab said on Twitter. Israel was trying to "change the rules of engagement," he said.
Israeli forces have been on alert along the northern border in anticipation of Hezbollah retaliation for the killing of one of its members a week ago in an alleged Israeli attack on the edge of the Syrian capital Damascus.
Controlled by Israel, the Shebaa Farms is claimed by Lebanon. The United Nations regards it as part of Syrian territory captured by Israel in the 1967 Six-Day-War.
Netanyahu has said any attacks from Lebanese territory will draw a powerful response. Hezbollah, which last fought a war with Israel in 2006, denied its forces had tried to cross the frontier and said the incident was "one-sided".
After the killing of two Hezbollah members in Damascus last August, the group's leader, Sayyed Hassan Nasrallah, vowed to respond if Israel killed any of its fighters in Syria. But Hezbollah's deputy leader said on Sunday all-out war with Israel was unlikely.
Hezbollah fighters deployed in Syria as part of Iranian-backed efforts to support President Bashar al-Assad. Israel sees the presence of Hezbollah and Iran in Syria as a strategic threat and has mounted raids on Iranian-linked targets.