JERUSALEM — The prime minister and defense minister of Israel have agreed to an Egyptian-brokered cease-fire with Hamas for the Gaza area starting Thursday, Israel Radio reported on Wednesday morning.

Egyptian and Hamas officials had already announced on Tuesday that a deal had been reached.

An unidentified senior Egyptian official told the state news agency MENA, "The Palestinian and Israeli sides have accepted the first stage of a reciprocal and simultaneous period of calm, starting in the Gaza Strip, from 0600 on Thursday."

Mahmoud Zahar, a leader of Hamas, the Islamist group that controls Gaza, confirmed at a news conference there on Tuesday evening that a truce was about to come into effect and that it would last for six months.

A senior Israeli defense ministry official, Amos Gilad, traveled to Cairo on Tuesday night to receive final clarifications from the Egyptians. On his return Wednesday morning, he told Israel Radio that an understanding had been achieved.

Maintaining a note of caution, Defense Minister Ehud Barak of Israel said on Tuesday that it was "difficult to determine how long" an agreement would last.

Events on Tuesday, meanwhile, showed that both sides were liable to fire up to the last minute. Israel carried out three airstrikes in Gaza against what the military described as "terrorist operatives." Six Palestinian militants were killed, according to medical officials in Gaza.

Hamas and a smaller, more radical group, Islamic Jihad, each said they reserved the right to respond. On Tuesday night, militants launched up to 10 rockets at Israel. Several fell in open areas around the Israeli border town of Sderot, a military spokeswoman said.

Islamic Jihad said four of the dead belonged to its military wing. But the Israeli military listed three of those killed as members of the Army of Islam, a small, shadowy organization inspired by Al Qaeda. The military identified one of the dead as Muataz Dagmush, 29, a senior member and a brother of the leader of the group.

The Army of Islam, along with Hamas, was involved in the capture of an Israeli corporal, Gilad Shalit, in a cross-border raid in June 2006. Corporal Shalit is still being held in Gaza.

Israel now seeks to halt the rocket and mortar fire from Gaza that has killed four Israeli civilians this year and has caused widespread trauma and disruption of life in Israeli towns and villages close to the Gaza border. In addition, Israel has insisted that any deal include an end to Hamas's military buildup in Gaza, and movement toward the release of Corporal Shalit.

Hamas wants an end to the frequent Israeli military strikes and incursions into Gaza, and an easing of the economic blockade that Israel has imposed since Hamas took over the area a year ago.

Mr. Zahar, the Hamas leader, said Israel would open the commercial crossings as soon as the truce came into effect. Two weeks later, he said, Egypt would host talks aimed at reopening the Rafah crossing on its border with Gaza. Mr. Zahar suggested that the Shalit case would be dealt with separately.

Israel, like the United States and the European Union, classifies Hamas as a terrorist organization and rejects any direct dealings with it. Israeli officials are therefore likely to portray any deal as an informal understanding in which Israel responds to calm with calm, rather than a negotiated agreement.

"Words are important, but deeds are more so," said Mark Regev, a spokesman for the Israeli prime minister. But he did not rule out further flexibility toward Hamas.

"If indeed there will be a total cessation of fire from Gaza, an end of the Hamas arms buildup and movement on Gilad Shalit's case, then there will be a very new situation," Mr. Regev said.

The Israeli government has come under increasing domestic pressure to chose either a broad military thrust aimed at stopping the rocket fire or an agreement for calm. Egypt has been mediating the matter for months. Last week, Israel's Security Cabinet opted to pursue the truce.

Haim Ramon, an Israeli vice premier, was one of four ministers who abstained in the cabinet vote. "I oppose the lull, because it's another victory for radical Islam," Mr. Ramon said Tuesday evening. "It won in Lebanon and now it will be winning in Gaza. So why be moderate? After all, why is Hamas seeking an agreement? Because this will be its chance to represent Gaza as the state of Hamastan."

Many Israelis fear that Hamas will use a period of quiet to regroup. But army officials have repeatedly warned that a military offensive could prove bloody and inconclusive.

Past understandings with the militant organizations have dissolved within months, with the smaller groups' never having been brought under control.

This time Israel is insisting that Hamas halt all fire from Gaza, and will hold it responsible for actions by smaller groups.

Taghreed El-Khodary contributed reporting from Gaza.