Militants opened fire on an international observer base near El Gorah, close to the borders of Israel and the Gaza Strip, and burned tires blocking a road to the camp, a witness and a security source reported Friday evening.
Several members of the force were reportedly wounded. Officials from the Multinational Force and Observers (MFO) in Cairo were unreachable Friday night.
Israeli media reported that some of the wounded were being evacuated to Soroka Medical Center in Beersheba for treatment. The IDF would not comment on reports that IDF helicopters were helping evacuate the wounded.
Egypt's Al-Masry Al-Youm reported that the gunmen attacked the base, setting fire to one of its guard towers and raised a black flag bearing Islamic inscriptions. Channel 2 described the attackers as Salafi Islamists, although that report was not confirmed.
The MFO is a force that was deployed to the Sinai Peninsula as part of the 1979 peace treaty between Jerusalem and Cairo. It includes a US contingent.
Earlier this year, dozens of armed Beduins surrounded an MFO base in a bid to release a number of people arrested by Egyptian authorities.
Fury about a film that insults the Prophet Mohammad tore across the Middle East after weekly prayers on Friday with protesters attacking US embassies and burning American flags as the Pentagon rushed to bolster security at its missions.
North of Sinai, at least 30,000 Palestinians staged rallies against the film, which denigrates the Prophet Mohammad.
Some 25,000 took to the streets of Gaza City, answering a call by Hamas and the smaller Islamic Jihad faction and waving the green and black flags of the two factions.
American and Israeli flags were set alight, along with an effigy of the film's producer.
In Nablus, in the northern West Bank, several hundred people protested and burned an American flag, witnesses said