An Israeli tank that killed a Reuters journalist and wounded six others in Lebanon last year fired two 120mm rounds at a group of “clearly identifiable journalists” in violation of international law, a UN investigation has found.

The investigation by the United Nations Interim Force in Lebanon (Unifil), summarized in a report seen by Reuters, said its personnel did not record any exchange of fire across the border between Israel and Lebanon for more than 40 minutes before the tank opened fire, killing Issam Abdallah, a 37-year-old video journalist.

“The firing at civilians, in this instance clearly identifiable journalists, constitutes a violation of UNSCR 1701 (2006) and international law,” the Unifil report said, referring to security council resolution 1701.

The seven-page report dated 27 February continued: “It is assessed that there was no exchange of fire across the Blue Line at the time of the incident. The reason for the strikes on the journalists is not known.”

Under resolution 1701, adopted in 2006 to bring an end to the war between Israel and Lebanese Hezbollah fighters, UN peacekeepers were deployed to monitor a ceasefire along the 120km (75-mile) demarcation line, or Blue Line, between Israel and Lebanon.

As part of their mission, UN troops record violations of the ceasefire and investigate the most egregious cases.

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Asked about the Unifil report, the Israel Defense Forces (IDF) spokesperson Nir Dinar said Hezbollah had attacked the IDF near the Israeli community of Hanita on 13 October. It responded with artillery and tank fire to remove the threat and subsequently received a report that journalists had been injured.

“The IDF deplores any injury to uninvolved parties, and does not deliberately shoot at civilians, including journalists,” Dinar said. “The IDF considers the freedom of the press to be of utmost importance while clarifying that being in a war zone is dangerous.”

He said the general staff’s fact finding and assessment mechanism, which is responsible for reviewing exceptional events, would continue to examine the incident.

Reuters’ editor-in-chief, Alessandra Galloni, has called on Israel to explain how the attack that killed Abdallah, 37, could have happened and to hold those responsible to account.

The Unifil report was sent to the United Nations in New York on 28 February and has been shared with the Lebanese and Israeli militaries, two people familiar with the matter said.

“[The] IDF should conduct an investigation into the incident and a full review of their procedures at the time to avoid a recurrence,” the report said in its recommendations. “The IDF should share their investigation’s findings with Unifil.”

A UN spokesperson confirmed that the Unifil report had been shared with the parties.

“We reiterate that all actors should uphold their obligations under international law, and that civilians, including journalists, should never be a target. Journalists and media professionals must be protected,” the spokesperson said.

For its investigation, Unifil sent a team to visit the site on 14 October, and also received contributions from the Lebanese Armed Forces and from an unnamed witness who was present on the hill when the strikes occurred, the report said.

Unifil’s findings lend further support to a Reuters investigation that showed that the seven journalists from Agence France-Presse, Al Jazeera and Reuters, were hit by two 120mm rounds fired by a tank 1.34km away in Israel.

The group of reporters had been filming cross-border shelling from a distance in open area on a hill near the Lebanese village of Alma al-Chaab for nearly an hour before the attack.