EL-ARISH, Egypt — Egypt’s military vowed on Monday to hunt down those behind the killing of its 16 soldiers at a checkpoint along the Sinai border with Israel. It called the attackers “enemies of the nation” who must be dealt with by force and suggested they were Egyptian Sinai-based militants who received Palestinian support from the Gaza Strip.
Security and military officials said at least two helicopter gunships arrived in the border town of El-Arish on Monday to join the hunt for the militants believed responsible. Israel meanwhile stepped up pressure on Egypt to clamp down on the lawless border region.
Israel says its aircraft killed eight militants who broke through the border after the killings. Egyptian officials have said six attackers were killed. A statement by the Egyptian armed forces said 35 militants took part in the attack, suggesting that close to 30 attackers may be on the run.
No group has yet claimed responsibility for the attack. Egypt and Israel say both Islamist militants from the Sinai and Palestinian allies from the neighboring Gaza Strip are active in northern Sinai, attacking both Egyptian security forces and staging raids across the border into Israel.
The armed forces statement suggested that groups on both sides of the border may have been involved.
“The armed forces have been careful in the past months and during the events of the (Egyptian) revolution (in 2011) not to shed Egyptian blood … but the group that staged yesterday’s attack is considered by the armed forces as enemies of the nation who must be dealt with by force,” said the statement.
In the first direct indication that the attackers may have had the help of Palestinian militants, the statement said “elements from the Gaza Strip” aided the attackers by shelling the Egyptian-Israeli border crossing of Karam Abu Salem with mortars as the attack was taking place.
The security and military officials said counter-terrorism units arrived in the border town of El-Arish on Monday and joint police-army patrols were combing the ground. Aircraft patrolled the sky overhead, they said.
The officials said the two attack helicopters were expected to be joined by more aircraft in the border zone, which has seen a surge of violence since Hosni Mubarak’s ouster last year.
The Sunday attack was one of the deadliest in the Sinai in years. Suspected Islamists attacked the checkpoint in the border town of Rafah at sunset, killing the soldiers as they were sitting down for the traditional meal breaking the fast in the holy month of Ramadan.
The attackers then commandeered two of their vehicles and burst through a security fence into Israel. Israeli officials say the incursion was quickly spotted and hit with an airstrike. The Egyptian military said only one armored vehicle was commandeered.
The unrest in Sinai poses a daunting challenge to Egypt’s Islamist President Mohammed Morsi, who since coming to office a little more than a month ago has warmed up to Gaza’s Hamas rulers. Hamas officials have condemned the killings, but Morsi may still come under pressure to back down from plans to end Egypt’s cooperation with the Israeli blockade of the Gaza Strip.
He vowed on Sunday night to make the killers pay for their crime and to restore security to Sinai, home to several of the most popular Red Sea resorts in Egypt. On Monday, he declared three days of mourning for the victims, according to state television.
“This is a huge calamity for Egypt,” declared his spokesman Yasser Ali.
The Sinai border has been largely quiet for most of the three decades since Israel and Egypt signed a peace agreement, although security forces have for years combated a low-level insurgency in El-Arish and nearby areas. The 1979 treaty restricts the number of troops and the type of weapons Egypt can deploy in the peninsula.