An Israeli strike killed a commander of Hezbollah's elite Radwan force in south Lebanon on Monday, according to security sources familiar with the group's operations in the country.
It's one of the most high-profile attacks on its senior officers in three months of hostilities with Israel.
Wissam Al Tawil, the deputy head of a Radwan unit, and another Hezbollah fighter were reportedly killed when the car they were in was struck in the village of Majdal Selm, some 6 km from the border.
One of the security sources called Tawil's death "a very painful strike". Another said, "things will flare up now."
Hezbollah says its campaign aims to support Palestinians in the Gaza Strip. The hostilities between the group and Israel have largely been contained to areas near the border.
Tensions spiked higher last week when an Israeli strike killed deputy Hamas chief Saleh al-Arouri in Beirut's southern suburbs, an area controlled by Hezbollah. Israel has neither confirmed nor denied its responsibility for that attack.
Hezbollah on Saturday said it had hit a key Israeli observation post with 62 rockets as a "preliminary response" to Arouri's killing.
Israeli planes and tanks pounded areas across the Gaza Strip overnight and on Sunday, destroying several residential buildings, witnesses said, as Palestinians desperately awaited implementation of a US plan to end the war.
The number of students confirmed dead after the collapse of a boarding school building in Indonesia rose to 36, from 16 a day earlier, the country's disaster mitigation agency said on Sunday.
President Donald Trump told Israel on Friday to immediately stop bombing Gaza after Hamas agreed to release hostages and accept some other terms in a US plan to end the war, but issues like disarmament appeared unresolved.
Russia rained missiles and drones on Ukraine in a mass overnight attack, officials said on Sunday, killing at least five people and damaging civilian infrastructure including energy facilities across numerous regions.