Israel agreed to Egypt-brokered truce but resumes bombing after Palestinian group says its demands were not met

Israel has resumed its bombardment of Gaza a few hours after agreeing to an Egyptian proposal to end the eight-day military confrontation with Hamas, and in response to continued rocket fire from the coastal enclave.

The Israeli security cabinet had agreed to a "de-escalation" of the conflict, to begin at 9am today, but Hamas rejected the proposal, saying it had not been consulted and its demands were not being met.

In a statement issued by his office, the Israeli prime minister, Binyamin Netanyahu, said: "Hamas's rejection of the ceasefire gives Israel full legitimacy to expand the operation to protect our people. No country would sit idly by while its civilian population is subjected to terrorist rocket fire. Israel is no exception."

According to the Israeli military, about 50 rockets were fired from Gaza into Israel in the six hours that Israel stopped air strikes. No one was injured.

There were numerous reports of explosions in Gaza following the announcement. The total death toll among Palestinians was expected to top 200 with the resumption of action.

Israel's deputy foreign minister, Danny Ayalon, suggested that Israel may escalate military action to include a ground invasion as well as aerial and sea bombardment. "If Hamas does not accept a ceasefire by 9pm tonight, my estimation is that the IDF [Israeli Defence Force] will have to enter," he tweeted.

However, there were signs of division within Hamas. Conflicting messages were delivered by the Hamas leadership within Gaza, and its international leadership. The organisation's military wing also took a more defiant stand than the political leadership.

The al-Qassam Brigades issued a robust rejection of the truce plan, saying: "Our battle with the enemy continues and will increase in ferocity and intensity." It described the proposal as a "surrender".

Hamas spokesmen in Gaza said the Islamist group had not received an official ceasefire proposal, and its demands must be met before it lays down its weapons.

But Mussa Abu Marzuk, a senior Hamas leader based in Cairo, wrote on Facebook that "we're still in consultations. The movement has yet to take an official position on the initiative," according to Agence France-Presse.

Although Egypt has been a key player in brokering ceasefires to end previous conflicts between Israel and Hamas, the Islamic leaders of Gaza deeply distrust the Cairo regime that has been in place since a military coup a year ago. President Abdel Fatah al-Sisi has outlawed the Muslim Brotherhood, Hamas's ideological parent organisation, and attitudes towards Gaza and its rulers have hardened.

Hamas and other Palestinian leaders are also likely to be suspicious of the role of Middle East envoy Tony Blair, who has been acting as an interlocutor between Israel and Egypt. Blair is seen as a staunch defender of Israel's interests and an enthusiast for Sisi's regime.

Hamas has set out its key demands for ending rocket fire, which include the lifting of Israel's eight-year blockade on the Gaza Strip, the opening of the Rafah border crossing with Egypt and the release of more than 50 Palestinian prisoners Israel recently rearrested after freeing them in exchange for kidnapped Israeli soldier Gilad Shalit in 2011.

The continuation of military action will dismay the US secretary of state, John Kerry, who had urged all parties to support a ceasefire. Speaking in Vienna before Israel resumed its air strikes, he said: "I cannot condemn strongly enough the actions of Hamas in so brazenly firing rockets in multiple numbers in the face of a goodwill effort to offer ceasefire."

However, he added: "I still think, perhaps, reason could prevail. If the political wing can deal with the military wing."

Egypt had proposed a 12-hour period of "de-escalation", to be followed by a full ceasefire and talks between the two parties and mediator on a long-term agreement.

Despite the resumption of action, Israel may be anxious about getting drawn deeper into a military confrontation in Gaza. There has been no loss of Israeli life in the past eight days, but the chances of civilian or military deaths increase the longer the fighting continues, especially in the event of a ground invasion.

Israel may also have calculated that its bombardment of Gaza has achieved its principal goal of weakening Hamas and punishing the people of the coastal enclave. It does not want to deal a fatal blow to Hamas, for fear that more radical groups would fill a power vacuum in Gaza.

Previous military confrontations between Israel and Hamas – Operation Pillar of Defence in November 2012, and Operation Cast Lead in 2008-09 – ended in ceasefire and negotiated agreements that eventually broke down. Most diplomats believe the cycle will continue unless the fundamental underlying causes of the wider Israeli-Palestinian conflict are addressed and resolved.