ARISH, Egypt, Jan. 30 -- The death toll of Thursday's mortar attacks that targeted security premises in Egypt's North Sinai province rose to 33, including 31 military men and two civilians, a security source told Xinhua.

"The injured people are being transferred from Arish to Cairo by ambulances for better treatment," the source added.

Later in the day, massive attacks using car-bombs and mortar shells targeted security premises in Arish and left tens killed and dozens injured. Attacks were extended to reach two big security checkpoints in nearby Rafah city.

The security source told Xinhua that "there were three car-bombs in last night's attacks in Arish, a water-supplying vehicle and two microbuses," the source added.

Meanwhile, the Egyptian forces raised security levels and strengthened troop deployment in the restive peninsula, and are currently combing the region for the perpetrators.

Earlier on Friday, two little children were killed and several others were injured in a fire exchange between the Egyptian army and Islamist militants in two villages in North Sinai.

Egyptian President Abdel-Fattah al-Sisi returned to Cairo from Addis Ababa on Friday as he decided to cut short his participation in the 24th African Union Summit held in Ethiopia in the aftermath of the attacks, official MENA news agency reported.

"We are all sad for what happened yesterday in Sinai, but Egypt is paying the price for its confrontation of terrorism and extremism," Sisi said before leaving the Ethiopian capital city.

Sisi added that the economic summit scheduled to be held in Sharm El-Sheikh in March will not be delayed, urging all Egyptians "to maintain a high spirit."

The funeral of the victims held in Cairo on Friday was led by Prime Minister Ibrahim Mahlab, Defense Minister Sedqi Sobhi, Interior Minister Mohamed Ibrahim as well as representatives from Al-Azhar Islamic institution and the Coptic Church and some family members of the victims.

Egypt has recently extended a curfew in many parts of North Sinai for another three months due to the unstable security situations in the area and the recurrent terrorist attacks targeting security men and premises.

The government has also been evacuating houses at the borderline with the Gaza Strip to create a buffer zone and intensify anti-terror military operations in the northern part of the peninsula.

The anti-security attacks mounted in Sinai and other parts across the country since the ouster of Islamist President Mohamed Morsi by the military in July 2013 and the following crackdown on his supporters that left about 1,000 killed and thousands more arrested.

So far, hundreds were killed in the attacks targeting security forces by militant groups. Most of the attacks were claimed by Sinai-based al-Qaida-inspired Ansar Bayt al-Maqdis group, which has recently changed its name to "Sinai State" after declaring loyalty to the Islamic State (IS) militant group in Iraq and Syria.

Since Morsi's removal, his loyalists have been staging anti-government protests denouncing Morsi's ouster as "a coup." The Muslim Brotherhood group, Morsi's power base, was blacklisted by the new leadership as "a terrorist organization."

On Friday, the police arrested tens of pro-Morsi protesters affiliated with the Brotherhood in the provinces Alexandria, Fayoum, Qena, Sharqiya and Gharbiya.

The Supreme Council for the Armed Forces said in a statement on Friday that it will continue securing all efforts to complete the country's post-Morsi future roadmap and restore security and stability to the country.

"We will continue intensifying raids and pursuits of all elements of terrorism and extremism in Sinai and nationwide in cooperation with the civil police and with the indefinite support of the masses of the great Egyptian people," said the statement.

After removing Morsi due to mass protests over his one-year rule, ex-military chief and now President Sisi announced a three-stage future roadmap including a new constitution, presidential and parliamentary elections.

The first two stages were fulfilled and the country is currently preparing for the parliamentary polls scheduled to be held from March 21 to May 7.