The Israeli military says Hezbollah has fired into a disputed border zone, the group's first attack since a ceasefire took hold last week.

Israel said it struck targets in Lebanon on Monday evening after vowing to retaliate for an attack by Hezbollah on a military post, with both sides accusing each other of violating last week's ceasefire. At least nine people were killed by Israeli strikes on two southern Lebanese villages, according to the country's public health ministry.

Hezbollah has claimed the first strike against Israel since a US-backed cease-fire plan came into effect less than a week ago, prompting Israeli officials to vow a strong response in the most serious threat so far to the truce with Lebanon.