Two leaders of the Palestinian Islamic Jihad (PIJ) were killed in airstrikes on the third day of combat between Israeli troops and militants in Gaza.

The head of PIJ's rocket launching force and two other militants were killed in a pre-dawn attack on an apartment in Khan Younis, while his deputy was killed in a strike in a nearby town later in the afternoon, the BBC reported.

Meanwhile, a rocket fired from Gaza hit a building in the central Israeli city of Rehovot, killing one person and marking the first fatality in Israel since the start of the operation against PIJ on Tuesday.

The Israeli military had launched a series of air strikes that killed three other commanders of the group. Health officials in Gaza reported that 28 people had been killed and 93 injured during the same period, including at least 10 civilians. The United Nations has condemned the civilian deaths as unacceptable.

As of 2:30 p.m. local time (7:30 a.m. ET), the Israel Defense Forces (IDF) reported that at least 547 rockets had been fired from Gaza towards Israel, in retaliation to the heavy airstrikes from the Israeli military, according to CNN.

Read Also: US Debt Ceiling: Treasury Secretary Yellen Suggests New System

Since Tuesday, the IDF has been targeting Islamic Jihad operatives and infrastructure in the strip, resulting in the deaths of four leaders of the Palestinian militant organization, including Ali Hassan Ghali, the Al-Quds Brigades Commander in charge of the rocket unit.

In total, 28 Palestinians have been killed and 86 injured since the airstrikes began on Tuesday morning, according to the Palestinian Ministry of Health in Gaza.

Ceasefire Efforts Fail

Although mediation efforts by Egypt had appeared to be leading towards a ceasefire on Wednesday night, fighting surged again on Thursday as Islamic Jihad presented several conditions for a ceasefire, including a halt to Israeli assassinations. Israeli officials, however, have not indicated a willingness to commit to such conditions.

Israeli Prime Minister Benjamin Netanyahu stated during a visit to an air defense battalion that whoever attacks Israel "will pay the price, as will his replacement," per The New York Times.

Rear Adm. Daniel Hagari, the chief spokesman of the Israeli military, explained that part of the difficulty in reaching a ceasefire was because exiled leaders of Islamic Jihad, residing in hotels in Beirut and Damascus and supported by Iran, were setting the agenda.

Related Article: Pakistan Supreme Court Deems Imran Khan's Arrest Illegal