Claim by Saleh al-Arouri, a founder of Hamas's military wing, is doubted by experts and not supported by other Hamas sources

A veteran Hamas official has said that the Islamist group was behind the kidnapping of three Israeli teenagers in the West Bank – an incident that was a major trigger for the current brutal war in Gaza.

Saleh al-Arouri, one of the founders of Hamas's military wing, made his comments at a conference in Istanbul, where he lives in exile. A tape of his comments was posted online by conference organisers.

"There was much speculation about this operation; some said it was a conspiracy," al-Arouri said at a meeting of the International Union of Islamic Scholars on Wednesday.

"The popular will was exercised throughout our occupied land, and culminated in the heroic operation by [Hamas's armed wing] the Qassam Brigades in imprisoning the three settlers in Hebron."

His claim has not been supported by any other member of Hamas.

It is the first time that any senior Hamas figure has linked the group to the abduction of Eyal Yifrah, 19, Gilad Shaar, 16, and Naftali Frenkel, 16, whose kidnapping and murder led to a spiral of violence that gripped Israel and the West Bank and culminated in the current war in Gaza, which has so far left more than 2,000 Palestinians and 64 Israeli soldiers dead, as well as two Israeli civilians and a Thai migrant worker.

Israel has always maintained that Hamas was behind the abduction, and launched a massive operation in the West Bank against the group in June and July, during which dozens of members were arrested. Hamas has so far refused to confirm or deny its involvement, and a spokesman could not be reached for comment on Thursday.

Al-Arouri's role in Hamas dates back to the 1990s, according to a US indictment issued in 2003, when he was a student at Hebron University. Amnesty International in 2012 described him as one of the founding members of the Qassam Brigades.

According to Matthew Levitt, an analyst with the Washington Institute, al-Arouri was forced to leave Israel in 2010 after serving more than 15 years in prison for actions related to his Hamas membership. He lived in exile in Syria until the unrest during the Arab spring, when he moved to Turkey.

Hugh Lovatt, Israel and Palestine coordinator at the European Council on Foreign Relations, said that while al-Arouri was a significant Hamas figure – serving as the group's most prominent representative in Turkey – the former militant could have an ulterior motive for making his claim.

"Given the timing I would be very suspicious about his claim. I still don't believe Hamas as an organisation and its upper echelons sanctioned the kidnappings – something that Israeli intelligence also believes," he said.

Lovatt said that al-Arouri may be trying to claim credit for the actions of others in an attempt to demonstrate his own continued sway in the West Bank and Hamas's ability to hit Israel after failing to secure significant concessions after six weeks of violence in Gaza.

"A second, more remote possibility, is that al-Arouri is telling the truth and that he has operated on his own initiative – a development with very worrying repercussions as it would imply a serious power struggle and splintering within Hamas," he said.

Reuters reported on Wednesday that the three teenagers, who had been hitch-hiking near the Israeli settlement of Gush Etzion, were shot ten times soon after being taken. The man believed to be the ringleader of the kidnapping, Hussam Qawasme, is in Israeli custody, but two others believed to be his accomplices are still at large. Last week, Israeli military bulldozed the homes of two of the men and damaged another.

The murders led to a revenge attack during which three rightwing Israelis kidnapped and murdered 17-year-old Mohammed Abu Khdeir, leading to some of the worst street violence in Jerusalem in a decade.