Israel launched an airstrike on southern Lebanon on Friday, killing Hassan Farhat, a commander of the Palestinian group Hamas, along with his son and daughter, according to Israeli military sources.

The strike, carried out in the southern Lebanese city of Sidon, was a targeted response to Farhat’s alleged involvement in a rocket attack on Safed last year that left several Israeli soldiers dead and wounded. The Israeli military vowed to take action against Hamas fighters “wherever they operate,” further testing the fragile ceasefire that halted last year’s war between Israel and Lebanese group Hezbollah.

While Hamas’ armed wing, the al-Qassam Brigades, claimed that Farhat was assassinated in his apartment and praised his “blessed contributions” in the confrontation with Israel, Iran-backed Hezbollah condemned the strike, describing the targeting of Sidon as evidence of an expansion of aggression intended to target all of Lebanon. Meanwhile, Lebanese Prime Minister Nawaf Salam’s office denounced the attack as a clear violation of the US-backed ceasefire, while US officials have backed Israel, blaming “terrorists” for the renewed hostilities.

Israel has struck the Hezbollah-controlled southern suburbs of Beirut twice, and rockets have been fired from Lebanon toward Israel on two separate occasions. Hezbollah has denied any involvement in the recent rocket fire, accusing the ceasefire sponsors of overlooking Israeli attacks.