CAIRO -- The death toll from a brazen attack on a border post in Egypt's western desert along the border with Libya has risen to 22 troops, including three officers, the military said Sunday.
The attack on Saturday was deadliest suffered by Egypt's military in recent history. President Abdel-Fattah el-Sissi, a former military chief called the assault a terrorist attack and said it would not go unpunished. He also declared a three-day mourning period.
The military spokesman, Brig. Gen. Mohammed Samir, posted the names of the dead on his official Facebook page. A military funeral is expected later Sunday.
"The heinous crime that took these brave souls and spilled their blood will not go unanswered," a statement from the presidency said. "Terrorism will be uprooted from every part of Egypt."
Gunmen armed with rocket-propelled grenades attacked the border post in the country's largest province al-Wadi al-Gedid, which straddles the Libyan and Sudanese borders, before sundown Saturday, causing an explosion in the ammunition warehouse. Three attackers were killed in brief clashes.
Egypt security forces have increasingly come under attack by militants since longtime ruler Hosni Mubarak was toppled by a 2011 uprising. The attacks spiked last summer after the military, then led by el-Sissi, toppled Islamist President Mohammed Morsi following days of mass protests demanding his resignation.
In the single worst attack on security forces, 25 members of the riot police were captured and executed in the Sinai Peninsula just over month after Morsi was ousted. Militants killed 16 soldiers along Egypt's borders with Gaza and Israel in 2012, during Morsi's presidency.
Authorities launched a sweeping crackdown against Morsi's supporters after his ouster last year, arresting thousands of people, including virtually the entire leadership of the Muslim Brotherhood, from which he hails. The government has declared the Brotherhood a terrorist group and accused it of orchestrating the wave of violence, a charge the group denies.
In a statement Sunday, a Brotherhood-led coalition condemned the attack on the border guard and accused the military of failing to stop such attacks because it is engaged in politics.
"They have deviated from their main duty, which is to protect the nation's borders," the statement said.
Egypt has been increasingly concerned about the turmoil in neighboring Libya following the 2011 revolt that toppled and killed Moammar Gadhafi. Security officials say militants have crossed into Egypt via its long desert borders and also smuggled in weapons looted from Gadhafi's arsenals.