4 Palestinians killed in Gaza explosion

The Israeli military said it fired in the area but denied using artillery or tanks. The house is near the Karni cargo crossing between Israel and Gaza, where Israeli tanks and troops have been massing during a three-week offensive, sometimes entering the territory.

The house belonged to Hamas activist Mohammed Harara, 26, who was killed, said relatives who saw the bodies at Gaza's Shifa Hospital. Also killed were his mother and two of his brothers, both in their 20s, said Gaza Hospital spokesman Dr. Jumah Sakah. A fifth person was initially thought to have been killed but hospital officials said that was a mistake.

On Thursday, the Israeli army dropped Arabic-language leaflets over Gaza City, warning that houses were potential targets. Israeli forces have mostly attacked government compounds and open areas where militants fire rockets at Israel.

Israeli air and ground forces also raided a Gaza refugee camp for a second day, killing three Palestinians.

The Israeli offensive began after Hamas-linked militants captured an Israeli soldier in a June 25 cross-border raid.

More than 100 Palestinians have been killed, the UN reported. Many of the victims were gunmen, but at least 16 were minors. Israeli forces have mostly attacked government compounds and open areas militants use to fire rockets toward Israel.

The offensive has continued even as Israel wages a new campaign in Lebanon against Hezbollah, which began July 12 after guerrillas crossed the border and captured two soldiers.

On Thursday, Israeli aircraft carried out a series of strikes against Palestinian militants in the Mughazi refugee camp in central Gaza, the army said. Two militants were killed and at least 15 people, many of them civilians, were wounded, Palestinian medical officials said.