According to Robert Dreyfuss, author of "Devil's Game: How the United States Helped Unleash Fundamentalist Islam":
"And beginning in 1967 through the late 1980s, Israel helped the Muslim Brotherhood establish itself in the occupied territories. It assisted Ahmed Yassin, the leader of the Brotherhood, in creating Hamas, betting that its Islamist character would weaken the PLO."
According to Charles Freeman, former US ambassador to Saudi Arabia, "Israel started Hamas. It was a project of Shin Bet [Isreali domestic intelligence agency], which had a feeling that they could use it to hem in the PLO."
New York Times Reporter David Shipler cites the Israeli military governor of Gaza as boasting that Israel expressly financed the fundamentalists against the PLO:
"Politically speaking, Islamic fundamentalists were sometimes regarded as useful to Israel, because they had conflicts with the secular supporters of the PLO. Violence between the two groups erupted occasionally on West Bank university campuses. Israeli military governor of the Gaza Strip, Brigadier General Yitzhak Segev, once told me how he had financed the Islamic movement as a counterweight to the PLO and the Communists. 'The Israeli Government gave me a budget and the military government gives to the mosques,' he said."
As Dreyfuss notes, "during the 1980s, the Muslim Brotherhood in Gaza and the West Bank did not support resistance to the Israeli occupation. Most of its energy went to fighting the PLO, especially its more left-wing factions, on university campuses."
After the Palestinian uprising of 1987, the PLO accused Hamas and Yassin of acting "with the direct support of reactionary Arab regimes... in collusion with the Israeli occupation."
Yasser Arafat complained to an Italian newspaper: "Hamas is a creation of Israel, which at the time of Prime Minister Shamir, gave them money and more than 700 institutions, among them schools, universities and mosques." Arafat also maintained that Israeli prime minister Rabin admitted to him in the presence of Hosni Mubarak that Israel had supported Hamas.