The White House said Wednesday it wanted "answers" from Israeli authorities after the discovery of mass graves at two Gaza hospitals destroyed in Israeli sieges.

Gaza's Civil Defense agency said the day prior that health workers uncovered nearly 340 bodies of people allegedly killed and buried by Israeli forces at the Nasser Hospital in Khan Yunis.

Around 30 bodies were reported found buried in two graves in the Al-Shifa hospital courtyard in Gaza City.

"We want answers," National Security Advisor Jake Sullivan told reporters. "We want to see this thoroughly and transparently investigated."

The discoveries prompted the United Nations to demand an independent probe into the situation, backed by the European Union.

Israeli army spokesman Major Nadav Shoshani said the grave at Nasser "was dug -- by Gazans -- a few months ago."

The Israeli army did acknowledge that "corpses buried by Palestinians" had been examined by soldiers searching for hostages, but did not directly address allegations that Israeli troops were behind the killings.

Hospitals, which have protection under international law, have repeatedly come under Israeli bombardment over more than six months of war in Gaza.

Israel has accused Palestinian militant group Hamas of using medical facilities as command centers and to hold hostages abducted during its attack on Israel on October 7 which set off the war. Hamas has denied the claims.

The October 7 attack resulted in the deaths of around 1,170 people in Israel, according to an AFP tally of Israeli official figures.

In retaliation, Israel launched a military offensive that has killed at least 34,262 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.

Israeli 'offensive action' in south Lebanon

Israeli forces are carrying out "offensive action" across southern Lebanon, Defence Minister Yoav Gallant said Wednesday without specifying whether ground troops had crossed the border.

"Many forces are deployed on the border and IDF (army) forces are carrying out offensive action currently throughout southern Lebanon," Gallant said in a statement.

He also claimed that "half of Hezbollah's commanders in southern Lebanon have been eliminated" in months of violence.

"The other half are in hiding and abandoning the field to IDF operations," he added without giving a specific number.

A spokesman for the United Nations Interim Force in Lebanon (UNIFIL) told AFP that "we didn't detect any ground crossing today."

The Israeli army said it had struck 40 Hezbollah targets in southern Lebanon.

"A short while ago, IDF (army) fighter jets and artillery struck approximately 40 Hezbollah terror targets" around Aita al-Shaab in southern Lebanon, including storage facilities and weaponry, it said.

The army said Hezbollah "has established dozens of terror means and infrastructures in the area" to attack Israel.

Lebanon's state-run National News Agency said Israel had carried out more than 13 strikes near Aita al-Shaab and surrounding villages.

"Israeli warplanes carried out... more than 13 air strikes targeting the outskirts of the towns of Aita al-Shaab, Ramya, Jabal Balat and Khallet Warda," it said.

The strikes came after the Iran-backed Hezbollah movement said it fired a fresh barrage of rockets across the border on Wednesday following a strike that killed two civilians which the group blamed on Israel.

The group had already fired rockets at northern Israel late on Tuesday "in response" to the civilian deaths.

"The targeting of civilians... cannot happen without a concrete response," Hezbollah member of parliament Hassan Fadlallah told Lebanon's National News Agency during a funeral procession in southern Lebanon.

"Let us make this enemy understand that... we are ready for any scenario," he added.

Cross-border exchanges of fire have flared between the Israeli army and Hezbollah since Hamas's October 7 attack on Israel triggered war in Gaza.

Hezbollah began near-daily attacks against Israel on October 8 in support of its Palestinian ally Hamas.

Since October 7, at least 380 people have been killed in Lebanon, mostly Hezbollah fighters but also 72 civilians, according to an AFP tally.

Israel says 11 soldiers and eight civilians have been killed on its side of the border.

Tens of thousands have been displaced on both sides of the border.

On January 2, a strike widely blamed on Israel killed Hamas's deputy leader Saleh al-Aruri in southern Beirut.

Aruri is the most high-profile Hamas figure to be killed during the war.