GAZA CITY, Gaza Strip — Israel has unleashed new airstrikes on Gaza, hitting multiple high-rise buildings — including the home of a Hamas field commander — and two border tunnels dug by militants.

Meanwhile, Hamas and other armed groups fired dozens of rockets toward Israel.

Israeli media reports that a rocket struck an empty school Tuesday in the coastal city of Ashkelon, not far from the Gaza Strip. Israel’s Home Front Command had ordered the closure of schools on Monday in the area surrounding the Gaza Strip, including Ashkelon.

The escalation early Tuesday was sparked by weeks of tensions in contested Jerusalem.

Gaza health officials said that 24 Palestinians have been killed in Gaza, most by airstrikes, since cross-border fighting erupted. They said nine children were among the dead.

The Israeli military said 15 of the dead were militants.

During the same period, Gaza militants fired more than 250 rockets toward Israel, injuring six Israeli civilians.

In a further sign of rising tensions, the Israeli military said it is sending troop reinforcements to the Gaza border.

An Egyptian intelligence official says Egypt is engaged in “intensive” talks with Israel and Gaza militants on reaching a cease-fire to end the latest round of fighting.

The official said the efforts began in late April as the situation in Jerusalem worsened. He said Israeli actions, including the recent storming of the Al-Aqsa mosque and the planed evictions of Palestinian families from their homes in an east Jerusalem neighborhood, have frustrated the mediators.