The bombing injured six international peacekeepers, including four Americans, who are in the region as part of a force that monitors a 1979 peace treaty between Egypt and Israel.

Pentagon press secretary Peter Cook said the deployment had been planned before the attack.

“This is not a response to what happened with that IED [Improvised Explosive Device] attack a few days ago,” Cook said.

“We’ve been in discussions with key stakeholders regarding plans to increase force protection since early August.”

Cook said that in addition to the troops, the Pentagon is sending medical equipment including surgical teams.

Egyptian security officials said the peacekeepers were hit by a bomb planted on a road leading from their base.

The officials said Islamic State militants had placed bombs there aimed at passing Egyptian troops.