More Rockets Into Israel After Israeli Raid Into Gaza

— -- Hamas continued to launch rockets into Israel today -- even after the Israeli military said ground troops entered northern Gaza to take out a number of missile launch sites.

Hamas said it fired four rockets at 6 a.m. local time today (11 p.m. Saturday ET) on Israel's Rehovot military base, and the Israel Defense Forces (IDF) said Israel's Iron Dome defenses intercepted a rocket above the city of Ashdod and three more above the city of Ramla.

Israel's move into Gaza -- launched early Sunday local time (Saturday evening ET -- came after weeks of growing tensions, nearly a week of escalating missile strikes from both sides, and after the U.N. Security Council urged the two sides to reach a ceasefire.

RELATED: Americans Flee Gaza Amid Unrest

The Israeli government said it hit northern Gaza "with great force" to prevent more Hamas rocket attacks. An IDF source told ABC News that several dozen Navy commandos -- its military equivalent of Navy SEALs -- went ashore in Gaza in small boats with surveillance planes and attack helicopters in support.

The commandos took out Hamas long-range rockets and launchers that had been targeting Israel's major cities, according to the source. When Hamas militants spotted them, they opened fire and four commandos suffered cuts and scrapes. All the militants were killed.

The IDF troops returned to Israel after the mission and no soldiers were left in Gaza, the Israeli military said. It's the first time Israel has used ground troops in Gaza since 2009, according to IDF spokesman Lieutenant-Commander Peter Lerner.

The Israeli naval commando raid in Gaza occurred in the Al-Sudaniya beach to the northwest of the Gaza Strip, Al Jazeera reported.

Lerner said the tipping point for a full-scale ground incursion into Gaza would be if the Iron Dome failed to intercept a Hamas rocket. He said Israel has destroyed only 20 percent of Hamas' rockets, which its military estimates to be 10,000 total.

The Israeli military has been saying for a couple of days that it is ready, and tens of thousands of troops have been mobilized in support of a potential ground invasion.

This morning, the IDF said it was dropping leaflets over northern Gaza warning residents to evacuate.

"To the residents of Beit Lahiya, The IDF intends to attack terrorists and terror infrastructures in the area east of Al-Atatra and Al-Salatin St., and in the area west and north of Ma'bscar Jabalyia," the leaflets read, according to an IDF spokesman. "Israel is currently attacking, and will continue to attack, every area from which rockets are being launched at its territory. The civilians are requested to evacuate their residences immediately and move by 12:00 PM today, south of Jabalyia Al-Badr via Shar'a Al-Faluja. The IDF's campaign is to be short and temporary. Those who fail to comply with the instructions will endanger their lives and the lives of their families. Beware."

The conflict had already escalated Saturday, with Hamas bombarding Tel Aviv with the most rockets yet, and Israel responding by pummeling the Gaza Strip.

The IDF said this morning that it targeted more than 20 sites in Gaza overnight and 10 rockets were launched from Gaza, with eight hitting remote parts of southern Israel and two failing to reach Israel.

Hamas has fired more than 800 rockets at Israel in five days, the IDF said early today, with approximately 635 reaching Israeli territory. Meanwhile, Israel has struck approximately 1,320 targets in Gaza, the IDF added.

Over the past several days of bombardment by Israeli missiles, at least 163 Palestinians have been killed, according to Palestinian officials.

One of the Israeli strikes hit a center for the disabled where Palestinians said two patients were killed and four people seriously injured. In a second attack, on Saturday evening, an Israeli warplane flattened the home of Gaza's police chief and damaged a nearby mosque as evening prayers ended, killing at least 18 people, officials said.