Hezbollah deputy chief Sheikh Naim Qassem has vowed that Israel will pay a high price whenever it starts a ground offensive in the Gaza Strip, saying that his Lebanon-based group already is "in the heart of the battle."

The comments by Qassem came as Israel shelled and made drone strikes in southern Lebanon and Hezbollah fired rockets and missiles toward Israel. Hezbollah said six of its fighters were killed Saturday, the highest daily toll since the violence began two weeks ago.

By Asher Kaufman, University of Notre Dame

Lebanon, which is teetering on the edge of economic and political collapse, risks becoming entangled in the escalating war between Israel and Hamas.

U.S. Defense Secretary Lloyd Austin announced late Saturday he was sending additional air defense systems to the Middle East as well as putting more troops on prepare-to-deploy orders.

Austin said the U.S. would be delivering a Terminal High Altitude Area Defense, or THAAD, battery along with additional Patriot missile defense system batteries “to locations throughout the region to increase force protection for U.S. troops.” Bases in Iraq and Syria have been repeatedly targeted by drones in the days since hundreds were killed in a hospital blast in Gaza, and the destroyer USS Carney intercepted land attack cruise missiles in the Red Sea shot from Yemen on Thursday.

Israeli warplanes struck targets across Gaza overnight and into Sunday, as well as two airports in Syria and a mosque in the occupied West Bank allegedly used by militants, as the two-week-old war with Hamas threatened to spiral into a broader conflict.

Israel has traded fire with Lebanon's Hezbollah on a near-daily basis since the war began, and tensions are soaring in the Israeli-occupied West Bank, where Israeli forces have battled militants in refugee camps and carried out two airstrikes in recent days.

Police in Cyprus said Saturday they arrested four Syrians on suspicion of setting off a small explosive device that caused no damage not far from Israeli Embassy in the capital Nicosia.

Police said the four, ranging in ages between 17 and 21, face charges of attempted destruction of property using explosives, possession and use of explosives and possession of a knife.

Egyptian President Abdel Fattah al-Sisi on Saturday suggested a "roadmap" to end the ongoing war between Israel and Hamas.

"I have invited you today to discuss... a roadmap... that would begin by guaranteeing the complete, secure, fast and sustainable flow of humanitarian aid to Gaza's residents, followed by immediate negotiations over pacification and a ceasefire," al-Sisi said at the opening of a summit in Cairo with the leaders of regional countries and senior Western officials.

U.S. Secretary of State Antony Blinken has said he welcomes the release of two U.S. hostages held by Hamas and shared in the families’ relief but noted there are many more captives, including children and elderly people.

Speaking to reporters, Blinken said he and President Joe Biden had been able to speak with the families of some of the hostages during their trips to the Middle East.

A group of Iranian-backed militias in Iraq said U.S. forces “must leave immediately” or their bases in Iraq and elsewhere in the region will continue to come under attack.

Militant groups have launched rocket and drone attacks in recent days against U.S. bases in Iraq and Syria, most of which were claimed by the Islamic Resistance in Iraq. The group has said the attacks are retaliation for Washington’s support of Israel and a warning not to intervene in the Israel-Hamas war.

Egypt is hosting dozens of regional leaders and senior Western officials for a summit on the war between Israel and Palestinian militant groups in Gaza.

The meeting on Saturday in Egypt’s New Administrative Capital, just east of Cairo, will discuss ways to de-escalate the fighting and seek a cease-fire amid mounting concerns about a regional conflict, Egypt's state-run media reported. Among those attending the summit are the leaders of Qatar, the United Arab Emirates and the Palestinian Authority.

More than 4,200 people have been displaced from villages in south Lebanon by clashes on the border with Israel, and local officials said Friday that they are ill-prepared for the much larger exodus that would ensue if the limited conflict escalates to an all-out war.

Some 1,500 of the displaced are staying in three schools in the coastal city of Tyre, about 20 kilometers (12 miles) north of the border.