An Israeli strike Friday killed two Hezbollah fighters near the border, a source close to the Lebanese group and Israel's military said, while drones broadcast anti-Hezbollah messages over south Lebanon.
Hezbollah has traded near-daily fire with Israeli forces in support of ally Hamas since the Palestinian militant group's October 7 attack on Israel triggered war in Gaza.
But fears of all-out war have skyrocketed after an Israeli strike on Beirut's southern suburbs last week killed Hezbollah's top military commander, just hours before the killing, blamed on Israel, of Hamas's political leader Ismail Haniyeh in Tehran.
Iran and Hezbollah have vowed revenge.
Hezbollah in separate statements Friday said two of its fighters were "martyred on the road to Jerusalem", the phrase it uses to refer to fighters killed by Israeli fire.
A source close to the Iran-backed group, requesting anonymity, said the pair were killed "in an Israeli strike in Naqura".
The Israeli army said in a statement that "two Hezbollah terrorists were identified exiting a military structure belonging" to the group in the Naqura area, adding that air forces "eliminated" the operatives.
Elsewhere in south Lebanon, residents and local journalists circulated footage they said showed an Israeli drone flying over the village of Kunin, broadcasting the message in Arabic that the cross-border violence "is thanks to Hezbollah and Hassan Nasrallah", the group's chief.
On Thursday evening, residents of the southern town of Bint Jbeil circulated similar videos in which the same message could be heard.
The source close to Hezbollah told AFP the videos were authentic, calling the messages "incitement" against the group.
Hezbollah said it launched a series of attacks on Israeli troops and positions on Friday, including "a volley of Katyusha rockets" and "Falaq rockets" targeting forces stationed in the border town of Kiryat Shmona, and "explosive-laden drones" at another base.
Some of the attacks came "in response to the assassinations and attacks that the Israeli enemy carried out", Hezbollah said, also mentioning Naqura.
Lebanon's official National News Agency reported Israeli strikes on several locations in south Lebanon on Friday.
Ten months of cross-border violence has killed some 561 people in Lebanon, most of them fighters but also including at least 116 civilians, according to an AFP tally.
On the Israeli side, including in the annexed Golan Heights, 22 soldiers and 26 civilians have been killed, according to army figures.
The violence has displaced more than 102,000 people in Lebanon, the International Organization for Migration said on Thursday, with tens of thousands also displaced across the border in Israel's north.