CAIRO — Egypt’s president vowed “terrorism will be uprooted” after militants killed 22 border troops in the deadliest strike on security forces since Mohammed Morsi’s ouster.

Gunmen attacked the post in western al-Wadi al-Jadid province, near the Libyan border, with small arms and a rocket- propelled grenade, setting off an ammunition depot, military spokesman Brigadier General Mohammed Samir said. Four soldiers were also wounded in the attack that occurred shortly before the breaking of the daily Ramadan fast Saturday.

President Abdel-Fattah El-Sisi, who led Morsi’s ouster last year and made security a linchpin of his presidential campaign, convened a meeting of the national defense council, which promised to respond to “a despicable terrorist act,” according to a statement. “Their precious blood will be avenged.” Officials declared a three-day mourning period.

The assault follows a spate of attacks on security forces around the country, which the government has blamed on terrorist groups and members of the outlawed Muslim Brotherhood. El-Sisi, who was appointed defense minister by Morsi, has pressed a campaign against Islamists, with much of the focus on the restive north of the Sinai peninsula. Human rights groups accuse his government of stifling peaceful dissent to restore a police state.

Egypt has grown increasingly wary of the unrest in Libya, which has been mired in turmoil since the ouster and killing of Moammar Gadhafi in 2011, with the central government unable to control feuding militias, including Islamists. Egyptian security forces have intercepted scores of weapons shipments being smuggled over the border from Libya, saying some were bound for Hamas-controlled Gaza.

El-Sisi has repeatedly warned that escalating militant violence, including gains by Islamic State extremists battling Iraqi forces, represent a danger to the region. The unrest in Egypt has also spread to the capital, Cairo, where several bombs exploded June 30 outside a presidential palace where El-Sisi works, killing two policemen.

Saturday’s attack struck the same border security post where militants killed six security personnel about two months ago, the state-run Al-Ahram reported on its website. The army spokesman said two vehicles laden with explosives were defused at the scene. The assault on the forces was the worst since El- Sisi was elected and the deadliest since August 2012, when militants killed at least 25 police in Sinai.

Egyptian forces along the porous border with Sudan were put on alert after the attack, the state-run Ahram Gate news agency said, citing a security official it didn’t identify.