CAIRO (AP) — Egypt celebrated the army's 2013 overthrow of an Islamist president with a new national holiday on Thursday, a day that also saw deadly militant attacks in Sinai and clashes with smugglers near the country's porous border with Libya.

In Cairo, warplanes flew overhead in honor of the holiday as supporters of President Abdel-Fattah el-Sissi — who as defense minister led the ouster of Mohammed Morsi three years ago — geared for rallies later in the day, after the breaking of the Ramadan dawn-to-dusk fast.

But the day was punctured by violence in Egypt's restive Sinai Peninsula, where Islamic militants gunned down a Christian priest and two members of the country's security forces in separate attacks, according to security and medical officials. Later Thursday, six members of Egypt's security forces, including two officers, were killed in gun battles with smugglers on the country's western border. Three others were wounded and later flown to a military hospital in the Egyptian capital for treatment.

The smugglers were trying to infiltrate from Libya, the military said in a statement, adding that an unspecified number of smugglers were also killed.

Egypt's border with Libya, where Islamic militants have found a foothold since the 2011 ouster and killing of Libyan dictator Moammar Gadhafi, has been a major supply line for weapons and militants for Islamic extremists fighting Egyptian security forces in Sinai.

The violence came after el-Sissi on Wednesday appealed to his country's security forces and agencies to stop anyone from "spoiling" the June 30 occasion. He did not elaborate, but he appeared to be referring to possible protests by Morsi supporters or militant attacks.

Back in 2013, millions of Egyptians took to the streets on June 30, to call for Morsi to step down, just a year after he took office as Egypt's first freely elected president.

El-Sissi announced Morsi's ouster on July 3, 2013, and authorities later detained thousands of Morsi supporters and banned his Muslim Brotherhood as a terrorist group. Morsi, who has since been in custody, has been sentenced to death in one trial and long prison terms in several others. He is appealing his conviction on a range of charges, including a prison break, leaking secret documents and conspiring with foreign terror groups against Egypt.

Thursday's holiday, which the government refers to as the "June 30 Revolution" and which it announced earlier this week, will be also marked with musical performances and free entry to museums.

In the ancient southern city of Luxor, hot-air balloons carrying Egyptian flags flew over pharaonic temples and authorities planned a parade along the Nile River.

"On this glorious day, I would like to assure you that we are working hard to realize the hopes of the Egyptian people for the better future they deserve," el-Sissi, elected to office two years ago, said in a pre-recorded address to the nation that was broadcast on Thursday.

"The June 30 Revolution reasserts the impossibility of imposing a status quo on the Egyptian people. Anyone who imagines that he can successfully do that is deluding himself," he said, alluding to Morsi's Muslim Brotherhood supporters.

Egyptian security forces have been battling militants for years in Sinai, but attacks have grown deadlier and more frequent after Morsi's ouster.

In Thursday's attacks, the priest, Mussa Azmy, was gunned down while walking in the city of el-Arish near his house. The Sinai affiliate of the Islamic State claimed responsibility for the killing in a brief statement posted on social media websites sympathetic to the extremist group. It said the priest was a "warrior against Muslims," but did not elaborate.

Outside the city's main hospital, a bomb blast killed one policeman and wounded two. And in a Sinai village near the border town of Rafah, a bomb blast badly wounded a soldier. The soldier was wounded again when an ambulance taking him to el-Arish, escorted by an armored vehicle, was ambushed by militants.

That ambush killed another soldier, the security officials said, speaking on condition of anonymity because they were not authorized to talk to reporters.

Associated Press writer Sarah El Deeb in Beirut contributed to this report.