Mobile phone footage appears to contradict claims by Israel’s army that it shot at “terrorists [in] suspicious vehicles” during a controversial attack.

The video was recovered from the phone of a Palestinian paramedic who was one of 15 humanitarian workers killed by Israeli forces in the attack on March 23, according to the United Nations and the Palestine Red Crescent Society (PRCS).

Accounts from Gaza suggest some of the group had their hands or feet tied and were executed with a shot to the head.

Their bodies were found in a “mass grave” following the incident, according to Jonathan Whittall, head of the UN office for the co-ordination of humanitarian affairs.

The Israel Defence Force (IDF) said it was investigating the footage, after initially claiming troops had fired on “suspicious” vehicles with no headlights or emergency signals. The IDF also claimed the area was an active combat zone.

In the footage, released by the PRCS, an ambulance and a fire vehicle with flashing red lights are clearly seen.