United Nations Secretary General Kofi Annan has expressed doubt over an Israel Defense Forces probe determining that the blast on a Gaza Strip beach last Friday that killed seven civilians was caused by a mine or explosive device, placed by Palestinians to prevent IDF troops from reaching the area.

In addition, New York-based advocacy group Human Rights Watch found that the scene and victims’ injuries “strongly supports the theory” that the blast was caused by an Israeli shell, based on its interviews with eyewitnesses, Palestinian security personnel and the injured.

In an interview published in the London-based Arabic language daily Al-Hayat, Annan regarded the IDF’s version of the events as “strange.” The IDF investigation team examining the incident concluded Tuesday “beyond all doubt” that the casualties were not the result of Israeli shelling.

The head of the IDF probe, Major Meir Klifi, said that it was likely the blast stemmed from a bomb placed by the Palestinians at the site or “some form of unexploded ordinance.” He added that the probe on the latter point was continuing.

Marc Garlasco, a former Pentagon “battle damage expert” associated with Human Rights Watch, who visited the site of the incident, said that “all the evidence points” to a “155mm Israeli land-based artillery shell” as the cause of the blast. Garlasco, a former U.S. intelligence officer and bomb expert, examined the scene and shrapnel removed from the victims. Garlasco told Haaretz that the crater matched those created by shells.

Human Rights Watch report also noted that the victims injuries were not characteristic of explosive charges, which usually hit the lower body.

Garlasco also called for an independent inquiry into the deaths, saying that physical evidence, including shell fragments, shrapnel and the type of injuries “made Israeli shelling easily the likeliest cause.”

Annan also expressed sorrow and shock over the Israel Air Force strike in the Gaza Strip on Tuesday, in which seven Palestinian civilians were killed. He did not raise the possibility of a UN investigation of the incidents.

The UN chief called on Israel to abide by international law, saying that restraint should be practiced to prevent targeting civilians.

He also condemned the launching of rockets at Israel, and expressed concern over internal Palestinian disputes.

The IDF was quick yesterday to reject the Rights Watch report, reiterating its Tuesday conclusions. Military sources said the group’s expert testimony regarding fragments of Israeli shells 200 yards from the blast site, is meaningless. The IDF has admitted to repeated shelling of the area in recent months including a series of shells shortly before the incident, some of which landed not far from the blast in question.

Klifi, yesterday accused the Palestinians of trying to undermine investigation of the incident. “It is likely that the Palestinians tried to obscure some evidence. They removed shrapnel from the injured shortly after the blast, but when we asked for the fragments for examination, we were told they had disappeared.”

The Knesset Foreign Affairs and Defense Committee yesterday backed the IDF findings on the incident.

Annan’s spokesman Steven Dujarric refuted reports that Annan plans to launch an international investigation into the Friday incident. “There is no plan to send a UN representative,” Dujarric said. “We are monitoring the debate in the region, and listening to the charges and versions of both sides, but there is no plan to send a delegate or observer.”