Palestinian armed factions in the Gaza Strip are observing a 24-hour halt to rocket fire against Israel at the request of Egyptian mediators, a senior official of the ruling Islamist Hamas group said on Monday.

The announcement was released just as a Qassam rocket launched by Gaza militants exploded in the western Negev. A mortar shell and another rocket struck the area hours later. There were no reports of injuries hours later.

Gaza gunmen also shot at Israel Defense Forces soldiers along the coastal territory's border Monday, according to Israel Radio. The troops subsequently returned fire. No one was wounded in the incident, which took place near the Sufa border crossing.

Also Monday, IDF troops detained two Palestinians who had infiltrated into Israel from Gaza near the Kissufim border crossing, Israel Radio reported.

The Hamas spokesman, Ayman Taha, said the brief cease-fire went into effect on Sunday evening. He said Hamas might consider a longer truce if Israel were to reciprocate by ceasing all military attacks in Gaza and lifting an embargo on the impoverished territory.

In an interview with Israel's Channel 10 TV, Hamas leader Mahmoud Zahar said on Monday evening echoed Taha's remarks and the truce could be restored.

"The price is the lives of the Palestinian people," he said, demanding regular food and electricity supplies from Israel along with stopping Israeli military actions in the West Bank as well as Gaza.

Israel did not agree to halt operations in the West Bank under the truce that expired Friday, but Zahar's interview on an Israeli TV channel indicated that Hamas is interested in negotiating another cease-fire.

An Egyptian Foreign Ministry spokesman said Hamas' declaration that ther truce was being held upon Cairo's request was "not true at all."

Israel also voiced skepticism. "A ceasefire cannot be unilateral and Hamas, through its actions, has torpedoed the calm in the south," said Mark Regev, spokesman for Prime Minister Ehud Olmert.

A six-month Egyptian-brokered truce between Israel and Hamas expired on Friday with exchanges of fire across the border, raising fears of a wider conflict.

Hamas spokesman Tahar told Reuters that "Hamas and other factions agreed [to a one-day truce] in order to give a chance to the Egyptian mediation and to show that the problem was always on the Israeli side."

"If a new [truce] offer were made, which met our demands, then we would be willing to study it."

The surge of Palestinian rocket fire and Israel Air Force strikes over the weekend prompted calls in Israel to launch a wider offensive in Gaza.

Taha said any such escalation would be met by Palestinian retaliation including suicide bombings inside Israel.

An Israel Defense Forces spokesman said that, as of Sunday evening, Palestinians in Gaza had fired at least one rocket and four mortar bombs across the border.

Meanwhile, Palestinian Authority sources told Haaretz earlier Monday that Hamas has not given Egypt any signals that it is interested in renewing a cease-fire between Israel and the Gaza Strip.

The sources, who recently held talks with officials in Cairo, said Hamas has apparently not asked Egypt to renew its mediation efforts on the truce, which began in June and collapsed last Friday following numerous breaches.

Palestinian President Mahmoud Abbas is expected to visit Egypt on Tuesday for a series of meetings with senior officials, on issues including the cease-fire agreement and internal Palestinian dialogue.

Barak: Israel won't accept continued rocket fire

Defense Minister Ehud Barak, who has drawn criticism for his perceived reluctance to launch a massive military operation into Gaza, also said earlier Monday that Israel would not accept the continuation of rocket fire on its southern communities from Palestinian terrorists in Gaza.

The six-month truce between Israel and Gaza rulers Hamas ended late last week, when Hamas announced it would not be renewing the cease-fire.

"We have no intention of accepting the situation as it is developing in Gaza and we have no intention of accepting a continuation of fire on the Gaza envelope communities," Barak told a meeting of the Labor Party's Knesset faction.

The defense minister also called for an end to the speculative "chatter" about any Israeli military action in Gaza, which he said was interfering with IDF planning and the army's capabilities and effectiveness, which in turn would extract a higher price.

Meanwhile, one of Barak's Labor Party colleagues said Monday that Israel might be ready to consider a new truce with Hamas, in an apparent change of tone since the cease-fire ended.

Welfare Minister Isaac Herzog, a member of Prime Minister Ehud Olmert's security cabinet, questioned the long-term efficacy of any major military sweep of the crowded and impoverished coastal strip, and said renewing the truce, originally brokered by Egypt, could be an option.

"The calm is, of course, one alternative, and it is an alternative that can be seriously examined," Herzog told Israel Radio. "I, like many of my colleagues, am ready to consider continuing the calm, on terms that are comfortable for Israel."

Asked whether this might be broached with Hamas, Herzog said: "No, I don't think we can open negotiations. Right now we are dealing with an enemy who is not looking for negotiations."

Israeli officials are split on a response to the rockets which have pounded areas of the south over the past week. Both Barak and Olmert continued to urge restraint on Sunday, but Foreign Minister Tzipi Livni, who replaced Olmert as Kadima's head, and opposition leader Benjamin Netanyahu, who heads Likud, argued that Israel must get rid of the Hamas-run government. Israelis in the Qassam-hit communities have accused politicians of acting with an eye on the upcoming general elections.

While it seems that Israel's government has still not decided on a course of action regarding Gaza, it has nonetheless kicked off a public relations campaign with the intention of widening a basis for international support of a military offensive.

No Gaza orders yet

Meanwhile, senior IDF officers told Haaretz on Sunday that the army has not been ordered to make any preparations for a major operation in the Gaza Strip, but did not rule out the possibility of a future offensive.

Th Gaza Division has received no orders for any ground operations, said the officials, despite Barak's announcement Sunday that he has instructed the defense establishment to prepare for an offensive on Gaza in light of the escalating rocket fire from the coastal territory.

The officials said that as of now, offensive efforts would be waged mainly from the air. However, they added, a ground operation could be launched in the future if Hamas escalates from relatively small-scale attacks on border regions to large-scale rocket attacks deeper inside Israel.

The IDF is, nonetheless, increasing its level of readiness. In particular, the Home Front Command has worked hard over the past two weeks to improve rocket alert systems in communities located 30 to 40 kilometers from the Strip. It has systematically examined the warning systems in those communities and installed sirens in locations that lacked them, including educational institutions.

It also sent explanatory letters to residents and distributed 12,000 beepers to notify people of "Color Red" alerts whenever a Qassam is fired.

Nineteen rockets struck the western Negev on Sunday, following a barrage of 13 rockets and 20 rounds of mortar shells on Saturday alone.