Hamas said the explanation was part of its 52-page response to a U.N. report on last year’s Gaza war by a panel led by jurist Richard Goldstone, which accused it of targeting civilians by firing hundreds of rockets on Israeli communities.

“The killing of three Israeli civilians as alleged by Israel and as mentioned in the Goldstone report was by mistake and the target was military installations inside the Zionist cities,” said Salah al-Bardaweel, a senior Hamas official.

“Resistance fighters were warned against hitting civilians.”

However, New York-based Human Rights Watch rejected the Islamists’ claim of unintentionally targeting civilians and even noted comments by Hamas leaders during the three-week conflict that said attacks against Israeli civilians were acceptable.

“Hamas’s claim that rockets were intended to hit Israeli military targets and only accidentally harmed civilians is belied by the facts,” the rights group said.

Yigal Palmor of Israel’s Foreign Ministry said the Hamas explanation was “an absurd attempt to delude world opinion”.

This is the first time a leader of Hamas has described attacks in which Israeli civilians have died as mistakes. The group is responsible for the deaths of hundreds of Israeli civilians in suicide bombings since the 1990s.

A Hamas official who declined to be named defended past suicide attacks as a justifiable “response to the killing of Palestinian civilians throughout years of Israeli occupation”.

Hamas has also made no apology for firing thousands of inaccurate homemade rockets at southern Israeli towns over the past few years. Though most cause no injuries, the salvoes disrupt daily life and some of them are lethal.

Hamas and other militant groups in Gaza fired hundreds of rockets that hit Israeli communities in the Gaza war.

The Goldstone report criticizes both sides in last year’s Dec. 27-Jan. 18 conflict, which killed up to 1,387 Palestinians, including hundreds of civilians, and 13 Israelis, including the three civilians in question. But it was harsher towards Israel.

Israel boycotted the U.N. panel and also rejected allegations that it committed war crimes, also saying its forces had tried to minimise civilian casualties, in heavily populated areas in the Gaza Strip where militants operated.

The Goldstone report gives Israel and Palestinian Hamas militants six months to mount credible investigations or face possible war crimes prosecution in The Hague.

Cabinet minister Yuli Edelstein said on Sunday Israel would make do with internal army investigations of last year’s war that resulted in a handful of courts-martial over minor offences, but would deliver a “formal response” to the report.