JERUSALEM - Three Israeli soldiers were killed in a rare burst of violence along Israel's border with Egypt on Saturday, Israeli officials said.

Egypt and Israel both identified the suspected gunman as a member of the Egyptian security forces, though they gave differing accounts of what Egyptian authorities called an "accident" and Israeli authorities described as a "serious attack."

Two of the soldiers were found dead at a remote guard post early Saturday, officials said, just hours after Israeli forces had thwarted a drug-smuggling attempt in the area, a rugged and unpopulated stretch of the Negev desert. After an extensive search, the suspected gunman was killed in a firefight, along with a third Israeli soldier.

Israel Defense Forces officials said they were investigating the incidents in coordination with the Egyptian military.

All of the events occurred on the Israeli side of the frontier, officials said.

"Our assumption is that this was connected to the drug-smuggling attempt, but we can't be sure yet," Lt. Col Richard Hecht said in a briefing with reporters. "It could be [the Islamic State, the terrorist group active in Egypt's Sinai region], it could be a rogue border guard, it could be a smuggler, we're still looking into it."

Hecht said that "cooperation with Egypt is good, it's ongoing. This is not a geopolitical incident."

"We are in a joint investigation with the Egyptians, and it will be sharp, clear, and we will not leave any question unsolved," Maj. Gen. Eliezer Toledano, head of the Israeli military's Southern Command, told reporters during a visit to the Egyptian border, the Times of Israel reported.

In a statement posted to Twitter on Saturday night, Israeli President Isaac Herzog offered condolences to the families of the soldiers who were killed and vowed to "preserve their memory and continue to defend our borders with determination."

Egyptian and Israeli authorities gave conflicting accounts of the morning's events, with the Egyptian Army asserting the incident had resulted from a hot pursuit of drug smugglers.

"On Saturday early morning on June 3rd, 2023, a member of the security forces that are responsible for securing the international border line chased members of a drug smuggling [chain]," the military said in a statement Saturday afternoon. "During the chase a member of security forces breached the security checkpoint and exchanged fire which led to the death of 3 members of the Israeli security forces."

Hecht, the Israeli official, said the events of "a confusing morning" may have begun between 2 a.m. and 3 a.m. when Israeli soldiers foiled a smuggling attempt in which operatives on one side of the border barrier reportedly used ladders to pass contraband to the other. About $401,000 worth of illegal drugs were confiscated, the military said.

Several hours later, after two soldiers stationed at a guard post in the area failed to respond to radio communications, an officer arrived to investigate and found both had been shot, Hecht said. One was male, the other female. In a news release later Saturday, the IDF identified the female soldier who was killed as Sgt. Lia Ben nun, 19, a combat soldier from the central Israeli city of Rishon LeZion. She was promoted posthumously to the rank of corporal.

The Israeli military believes an assailant, acting alone, entered through a small gate Israeli forces use to cross the border in emergency situations, Israeli media reported.

Israeli forces launched a search of the area and tracked the suspected assailant, Hecht said. The man, who was armed with an automatic weapon, opened fire on Israeli troops, killing a male soldier. Israeli forces returned fire, Hecht said, killing the man.

The IDF identified the soldier killed in the exchange of fire as Sgt. Ohad Dahan, 20, from the southern city of Ofakim. He was promoted to the rank of staff sergeant after his death, the IDF said in a news release Saturday evening.

Egyptian Defense Minister Mohamed Zaki spoke with Israeli Defense Minister Yoav Gallant by phone to "discuss the circumstances of today's accident, offer condolences to the victims of the accident on both sides and coordinate jointly to take the necessary measures to prevent the recurrence of such incidents in the future," the Egyptian army said in a statement later Saturday.

Gallant, meanwhile, referred to the incident as a "serious attack," and said that he and his counterpart had agreed to "prevent terrorism in the border area and to strengthen security relations."

The incidents took place near the Nitzana border crossing, about 25 miles from the converging frontiers of Israel, Egypt and the Gaza Strip. Goods from Egypt destined for Israel or the Gaza Strip are imported through the crossing.

Israel completed a 250-mile border wall in 2014, with the aim of preventing illegal immigration, drug and arms trafficking and incursions by militants coming from Egypt.

Israel's Egyptian frontier has been a relatively calm frontier in recent years, although smuggling attempts into Israel are not unusual, officials said.

Israel and Egypt signed a peace agreement in 1979. Under Egyptian President Abdel Fatah El-Sisi, who rose to power following the 2013 military coup, Cairo has cooperated closely with Israel on security, particularly in the Sinai Peninsula.

Parker reported from Paris. The Washington Post's Sarah Dadouch in Beirut contributed to this report.