A commander in Hamas's military wing was killed early Thursday in an ISIS suicide bombing at the Rafah border crossing, which connects the Gaza Strip and Egypt.
According to the Gazan Interior Ministry, Hamas forces stopped for a security check two people who were nearing the border crossing from inside the strip when one of them set off an explosion, likely from a suicide belt.
The commander who was killed was identified as 28-year-old Nidal al-Jaafari, who in addition to being a member of the Izz ad-Din al-Qassam Brigades also served in the Hamas security forces.
Five other Hamas security personnel suffered various degrees of injuries in the explosion. The second terrorist was also wounded. The wounded were taken to the Abu Yousef al-Najjar hospital in the strip.
The two terrorists are members of the Salafist faction in the Gaza Strip, which is affiliated with ISIS.
It marked the first time that Hamas, which has carried out scores of suicide attacks over the years targeting Israelis, was itself targeted in such an assault.
Hamas has recently stepped up patrols in the border area with the declared aim of preventing the movement of so-called Jihadist Salafis between the territory and the Sinai peninsula, where Islamic State has been battling Egyptian troops for years.
The Hamas Interior Ministry described the assailant and his colleague as "ideologically deviant," a term Hamas uses to describe members of the Islamic State group and other extremists.
Hamas's military wing, the Izz ad-Din al-Qassam Brigades, vowed in a statement to "fight the alien deviant ideology without concession."
The family of the attacker issued a statement condemning what he did, offering condolences to the security officer's family and refusing to hold mourning observances. Family members claimed Qualleb tried to infiltrate Egypt along with the other terrorist and when the two of them were stopped, he blew himself up.
In the wake of the attack, Hamas security forces have increased their presence in the Rafah area, setting up dozens of checkpoints and searching cars.
"This is a significant turning point in Hamas's fight against the Salafists and other ISIS-affiliates in the Gaza Strip," a Gaza source told Ynet.
The source said the Palestinian factions in the strip are expected to convene on Thursday to discuss the ramifications of the attack.
The Rafah border crossing was opened on both sides for two days Wednesday morning to allow pilgrims to travel to Saudi Arabia for the Hajj and humanitarian cases to get through.
Hamas has sought to secure Gaza's borders in order to improve relations with neighboring Egypt, which is battling an Islamic State affiliate in the Sinai Peninsula bordering Gaza. Egypt keeps its border crossing with Gaza largely shut and has accused the group in the past of aiding militants in the Sinai. Hamas has denied those allegations.
"What happened at the strip shows that the cost of Hamas's decision to defend Egypt from the (Gaza) border is in blood. This attack with strengthen the security ties between Gaza and Cairo," a source close to Hamas said.
Reuters and the Associated Press contributed to this report.