The strikes in the southern town of Rafah came just hours after Israel bombed an apartment tower in Gaza City, collapsing the 12-story building with 44 apartments. Around 30 people were wounded in the strikes, but no one was killed, Palestinian officials said.

The targeting of large buildings appears to be part of a new military tactic by Israel. Over the weekend, the army began warning Gaza residents in automated phone calls that it would target buildings harboring "terrorist infrastructure" and that they should stay away.

A senior military official confirmed that Israel has a policy of striking at buildings containing Hamas operational centers or those from which military activities are launched. The official said each strike required prior approval from military lawyers and is carried out only after the local population is warned.

However, he said, there was now a widening of locations that the military can target. The official spoke on condition of anonymity because he was not permitted to discuss the matter with reporters.

In the 12-story apartment tower, the target was a fourth-floor apartment where Hamas ran an operations center, according to Israeli media. In the past, Israel has carried out pinpoint strikes, targeting apartments in high-rises with missiles, while leaving the buildings standing. However, this time a decision was made to bring down the entire tower, according to Channel 10, an Israeli TV station.

The military declined immediate comment when asked why it collapsed the entire building instead of striking a specific apartment.

Meanwhile, Gaza militants continued to fire rockets and mortar shells at Israel, including at least 10 on Sunday, the military said. That was in addition to more than 100 on Saturday, most aimed at southern Israel.

Elsewhere, five rockets were fired from Syria and fell in open areas in northern Israel. It was not immediately clear whether they were fired by pro-government forces or rebel groups.

Amid persistent violence, Egypt has urged Israel and the Palestinians to resume indirect talks in Cairo on a durable cease-fire, but stopped short of issuing invitations.

Several rounds of indirect talks between Israel and Hamas have collapsed, along with temporary cease-fires that accompanied them. The gaps between Israel and the Islamic militant group on a new border deal for blockaded Gaza remain vast, and there's no sign either is willing to budge.

The Israeli military said it had carried out some 20 strikes on Gaza since midnight Saturday.

In Rafah, Israeli aircraft bombed the seven-story Zourab building, which houses an office of the Hamas-run Interior Ministry. Witnesses said the building was leveled and that the strikes caused severe damage to nearby shops, homes and cars. It was not immediately clear if anyone was wounded or killed.

Another strike hit a nearby shopping center with dozens of shops, sparking a fire that gutted the two-story building and wounding seven people. After daybreak Sunday, smoke was still rising from the site as shop owners inspected the damage. Windows and doors had been blown out in nearby buildings.

The military said the two buildings were attacked because they housed facilities linked to militants, but did not provide details. The Gaza City apartment tower toppled Saturday was targeted because a Hamas command center operated from there, the army said. Twenty-two people were wounded in that strike.

Palestinian health official Ashraf al-Kidra, who confirmed the casualty figures for the strikes, said two people were killed in a pair of airstrikes near a coastal road on Sunday, including one on a group of people coming out of a mosque after morning prayers.

Two more fatalities were registered when a motorcycle following a car evacuating the wounded from the strikes was targeted, he said.

The U.N. estimates that more than 17,000 homes have been destroyed or damaged beyond repair since the war began on July 8. In some of the attacks, family homes with three or four floors were pulverized.

However, the weekend strikes marked the first time large buildings were toppled.

Since the fighting began, Israel has launched some 5,000 airstrikes at Gaza, while Gaza militants have fired close to 4,000 rockets and mortars, according to the Israeli military.

More than 2,100 Palestinians, including close to 500 children, have been killed, according to Palestinian health officials and U.N. figures. Israel has lost 64 soldiers and four civilians.

Israel says it is targeting sites linked to militants, including rocket launchers, command centers and weapons depots. The U.N. says about three-fourths of the Palestinians killed have been civilians.

The war stems from the kidnapping and killing of three Israeli teens in the West Bank by Hamas operatives in June, which triggered a massive Israeli arrest campaign in the West Bank, followed by an increase in rocket fire from Gaza.