UNICEF, the UN children's agency, called the figures "staggering" and stressed that under international humanitarian law, children had to be protected at all times during conflict.

And the World Health Organization (WHO) said more than 600 people had been killed in Lebanon since the ceasefire was supposed to have taken effect on April 17.

"According to the Lebanese Ministry of Public Health, 77 children have reportedly been killed or injured over the past week alone," UNICEF spokesman Ricardo Pires told a media briefing in Geneva.

"Fifteen children killed and 62 injured in seven days. That's an average of 11 children every 24 hours.

"We understand the vast majority of these children were impacted by airstrikes in south Lebanon. Only yesterday, seven children were killed and 30 injured," he said.

The ceasefire between Israel and the Iran-backed Lebanese group Hezbollah has never been strictly observed.

Both sides accuse each other of violating it and justify their attacks by the other camp's alleged breaches.

In total, since the ceasefire was announced, 55 children have been killed and 212 wounded, Pires said.

- Hospitals damaged -

Lebanon was drawn into the Middle East war in early March when Hezbollah launched rockets at Israel over the killing of Iran's supreme leader in US-Israeli attacks, prompting Israeli strikes and a ground invasion.

The WHO said there had been 1,774 injuries and 608 deaths in Lebanon from April 17 to May 22.

"The threat of expansion of military activities raises grave concerns for the health of the population," WHO spokesman Christian Lindmeier told the Geneva press conference.

"To date, in this conflict, a total of 16 hospitals and 13 primary healthcare centres have been damaged... Three hospitals remain closed," he said.

Israel's Prime Minister Benjamin Netanyahu said Friday that Israeli forces had crossed Lebanon's Litani River, which runs around 30 kilometres (19 miles) north of the countries' shared border.

Israel has bombed several bridges over the Litani in recent weeks -- effectively cutting off the area to the south from the rest of Lebanon -- accusing Hezbollah of using them to transport weapons and reinforcements.

Lindmeier said access to acute medical care and maternal health services south of the Litani "remains critically constrained".

Patients are facing "delays of up to 48 hours to secure clearance for movement to referral facilities, causing serious risks to patient outcomes, including increased maternal and neo-natal morbidity and mortality", he said.

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