An Israeli envoy engaging in Gaza cease-fire talks returned without a deal late Thursday, after another day of bloodshed in the coastal territory that included seven Palestinians being killed in a house explosion that Hamas blamed on an accident. When an explosion flattened a house in the Gaza Strip and killed seven, Hamas blamed Israel and unleashed rockets and mortar shells at southern Israel. But the militant group, which has controlled Gaza the past year, later suggested the blast was accidental. By then Israel had carried out an airstrike aimed at a Gaza rocket squad, killing a Palestinian. Two other Israeli military operations in Gaza killed five more militants.

Clashes in and around Gaza are putting a strain on Egypt's effort to arrange a truce by acting as a go-between because Israel has no contacts with Hamas, which has killed more than 250 Israelis in suicide attacks and rejects the Jewish state's right to exist.

Israeli officials said envoy Amos Gilad told Egyptian mediators in Cairo that Israel wants progress toward freeing a soldier captured by Hamas two years ago as well as a commit by Egypt to stop arms smuggling across its border with Gaza.

The officials, who spoke on condition of anonymity because the contacts are supposed to be private, said no agreement was reached Thursday.

With violence rising, Israeli government and security officials said Israel is willing to give Egyptian mediation about two more weeks to produce a truce, but warned that the military will be ready to invade Gaza if the effort fails.

Major points of contention remain, most prominently, Israel's demand to link the truce deal to the release of the Israeli soldier who has been held captive in Gaza for two years and a Hamas demand that Israel open Gaza's border crossings.

Israel blockaded Gaza a year ago after Hamas, which has killed hundreds of Israelis, violently seized control of Gaza from security forces affiliated with the moderate Palestinian president, Mahmoud Abbas.

The closure has prevented the vast majority of Gaza's 1.4 million people from leaving and has led to widespread shortages of fuel, electricity and basic goods.

After the Gaza house blew up Thursday, an Israeli army spokeswoman said the military was not operating in the area at the time. "We deny any connection to this incident," Maj. Avital Leibovich said.

Hamas spokesman Abu Obeida said there would be an investigation of the blast and the results would be made public.

The statement was taken as a Hamas acknowledgment that the blast was probably accidental, not an Israeli attack. Dozens of militants have been killed while handing explosives in recent years.

The blast shook the town of Beit Lahiya in northern Gaza, about a mile from the Israeli border. Cars parked nearby were destroyed and covered with dust, and windows of nearby houses and shops were shattered.

"It was a huge explosion," said Majid Abu Samra, a neighbor.

Hamas said seven people were killed, including a 4-month-old girl and a senior aide to the Hamas interior minister. Among the dead were five militants, Hamas said. The owner, Hamas area commander Ahmed Hamouda, was not home at the time of the explosion.

Shortly after the explosion, Hamas said it fired a barrage of mortar shells and rockets toward southern Israel in retaliation. Israel's rescue service said a 59-year-old woman was wounded when a rocket struck a home on an Israeli communal farm.

Mark Regev, an Israeli government spokesman, issued an angry response, noting the rocket barrage came just a day after Israel publicly endorsed the Egyptian truce effort. It proved that Hamas "is committed to violence, terror and murder," he said.

Israeli soldiers killed two Palestinian militants in a clash in northern Gaza, and Dr. Moaiya Hassanain of the Gaza Health Ministry said another person was killed by an Israeli airstrike in southern Gaza. The Israeli military said aircraft hit a rocket squad.

Late Thursday, three Hamas militants were killed by Israeli artillery fire that hit northern Gaza, Hassanain said. The Israeli military had no immediate comment.