Nearly a month into the Middle East war, the United Nations refugee agency warned that Lebanon was facing a deepening humanitarian crisis that risks teetering into a catastrophe.

Lebanon was pulled into the Middle East war when Tehran-backed militant group Hezbollah fired rockets towards Israel on March 2 to avenge the US-Israeli killing of Iran's supreme leader Ayatollah Ali Khamenei.

Israel has responded with large-scale airstrikes on Lebanon and a ground offensive in the south.

Lebanon's state-run National News Agency (NNA) reported an Israeli strike on south Beirut's Tahouitet al-Ghadir area, where authorities said another raid without warning earlier Friday killed two people.

AFPTV footage showed smoke rising from the area, a Hezbollah stronghold that has largely emptied of residents after previous Israeli army evacuation warnings and heavy strikes.

In the evening, the NNA reported a further strike elsewhere in south Beirut.

Israel's military said it had "begun a wave of strikes targeting Hezbollah terror infrastructure in Beirut" and issued an evacuation warning for several neighbourhoods in the southern suburbs.

The NNA also reported Israel strikes on the country's south and east.

In an updated toll, the health ministry said a raid on the town of Saksakiyeh in south Lebanon's Sidon district killed six people including three children, and wounded 17 other people.

It also said a strike in the Bekaa region in the country's east wounded seven people and "killed a woman who was pregnant with twins".

- 'Extremely worrying' -

Hezbollah announced a series of attacks, including claiming its fighters had launched a surface-to-air missile at an Israeli warplane over Beirut.

In south Lebanon, Hezbollah said its fighters had clashed with "Israeli enemy army forces in the villages of Bayada and Shamaa at point-blank range with light and medium weapons".

Lebanon's coastal village of Bayada, adjacent to Shamaa, lies eight kilometres (around five miles) from the frontier.

The group also claimed responsibility for attacks on Israeli targets across the border.

AFP was unable to independently the claims.

Israel's army said it had found weapons including anti-tank missiles in a school in Khiam, a strategic border town where Hezbollah has reported repeated clashes with Israeli troops.

Israeli forces are pushing into numerous towns in southern Lebanon, aiming to create a security zone reaching the Litani River, some 30 kilometres from the border, to drive Hezbollah back and to protect northern Israeli communities.

Israeli army spokesperson Effie Defrin said that "contrary to the declaration by the Lebanese government earlier this year -- Hezbollah is still operating and conducting attacks from southern Lebanon."

"If the Lebanese government will not disarm Hezbollah, the IDF will," he said, referring to the Israeli armed forces.

Lebanese authorities say more than 1,100 people have been killed and more than one million others have been displaced, including some 136,000 staying in collective shelters.

The United Nations refugee agency's representative in Lebanon, Karolina Lindholm Billing, warned that "the situation remains extremely worrying and the risk of a humanitarian catastrophe... is real."

Nicolas Von Arx, regional director of the International Committee of the Red Cross, warned that "the humanitarian situation is worsening and civilians, as usual, are paying the highest price" in Lebanon.

After meeting Lebanese President Joseph Aoun, he said that "civilians must be protected wherever they are, whether they remain in their homes or are forced to flee".