Sinn Féin President Gerry Adams entered the Gaza Strip on Wednesday after former British Prime Minister Tony Blair was forced to intervene to enable the visit.
The Israeli Foreign Ministry had sought to block the visit because he was unwilling to promise not to meet with representatives of the government in Gaza.
It was concerned that high profile meetings of international politicians with Hamas would “grant the organization legitimacy”.
Defense officials said the decision to allow Mr Adams into Gaza was taken after Blair, currently an envoy to the Middle East, brought a personal request to him.
Mr Adams held a meeting with Palestinian prime minister Ismail Haniya and later attended a press conference among buildings ruined in the recent Israeli occupation.
Mr Adams said the Israeli blockade on building materials had to end and negotiations entered into with Hamas.
“This is a total denial of the rights of the people of Palestine. This is an open-air prison,” he said.
“People can’t travel out of here, they can’t travel in.”
Britain and the United States say that dialogue cannot be permitted until Hamas recognises Israel, renounces violence and accepts interim peace agreements.
Mr Adams compared the border crossing from Israel into Gaza to entering an airport.
“It was distinctly like being back in prison...you had to go through air-locked areas and so on,” he said.
Mr Adams described a scene of devastation, ruined hospitals, schools and homes and said he urged peace on the Hamas leadership.
“There should be a complete cessation of hostilities by all sides and I stressed our opinion that dialogue is central to whats required and that is the only way forward,” he added.
“The refusal to recognise the outcome of the ballot box in the Palestinian territories is also bizarre, that they challenge people to go into elections and then when they go into elections they don’t recognise it.”
He said the ordinary people of Israel “didn’t cause the problem” and were interested in a just peace settlement.
“The international community has a huge responsibility to use its influence to support a meaningful peace process that can deliver real change and hope for the people of Gaza.
“I am convinced following my conversations and from my knowledge of this situation that the overwhelming majority of Palestinians and Israelis want peace and stability and a better future.”