The Islamic Jihad terrorist group said four of its members were killed Saturday in a "work accident" in the southern Gaza Strip along the border with Israel.
The explosion struck a three-wheeled vehicle near one of the five protest camps Palestinians have set up along the volatile Gaza-Israel border in recent weeks.
The group said in a statement that it was "mourning its fighters who were martyred during preparations."
The group usually uses these terms to refer to casualties caused by the accidental detonation of weapons or explosives meant to be used in attacks against Israel.
The Gaza Health Ministry confirmed four fatalities in the incident. Medics at the scene in the Rafah area said the explosion was caused by Israel, but an Israeli military spokesman said the army was not involved.
"Contrary to reports currently circulating, I can tell you that the IDF is not aware of any IDF fire in the area surrounding Rafah," the spokesman said.
The blast came one day after a mass gathering along the border area in which thousands of Palestinians rioted, some burning tires and Israeli flags. The event was part of weekly mass protests on the border organized by Hamas, the rulers of Gaza.
Israel has accused Hamas and other terrorist groups of using the "March of Return" protests as a cover for attacks against Israel, and says its snipers have only targeted "main instigators."
One rioter was killed Friday, bringing the death toll to at least 30 over the last two weeks, with more than 1,500 wounded by Israeli fire since March 30. The IDF has identified at least 10 of those killed as known terrorists.
Hamas leaders have sent mixed signals about whether they plan an eventual mass breach of the border fence. The protests are to culminate in a large rally on May 15, the 70th anniversary of Israel's establishment.
Palestinians commemorate the Nakba, or displacement of Palestinian refugees during Israel's War of Independence on May 15, Nakba Day, the day after Israel declared its independence.
