Five people, including three children, were killed in southern Lebanon on Sunday in an Israeli airstrike targeting a Hezbollah operative, though claims that US citizens were among the dead are disputed.

Israel expressed regret over civilian casualties, while Lebanese officials condemned the strike as a “massacre” and a violation of international law.

UNICEF called the deaths of children “unconscionable,” and Lebanon’s President Joseph Aoun urged the international community to act against Israel’s continued violations of the ceasefire agreement with Hezbollah, CNN has reported.

The attack follows Israeli claims of victories against Hezbollah and ongoing tensions in the region.