Drawing little notice during a period of dramatic developments in Cairo, the militants have become increasingly bold and visible amid a broader breakdown of security in the strategically important desert, a buffer zone between Israel and Egypt. The eclipse of authority has also given rise to Sharia courts run by Islamic scholars who settle disputes according to Islamic law.

The Egyptian government’s failure to restore order in the Sinai has unnerved Israel, in part because of a recent attack on an Israeli border post. Some local residents worry that Israel might ultimately respond unilaterally, a prospect that alarms those who survived successive wars in the Sinai between the neighbors in the 1960s and 1970s. …

U.S. officials have grown increasingly concerned about deteriorating security in the Sinai. The subject is all but certain to come up during Secretary of State Hillary Rodham Clinton’s visit to Cairo this weekend, particularly because two U.S. citizens were reportedly kidnapped in the area Friday.