Egypt's army and police stepped up roadblocks in an area of northern Sinai as they tried to track down militant Islamists who kidnapped seven security officers last week, a security source said on Tuesday.
The militants seized the men on a road between the towns of el-Arish and Rafah near the border with Gaza on Thursday, in a challenge to the government's failing efforts to impose its authority in the lawless Sinai.
The desert region on Egypt's border with Israel has slipped further into anarchy since president Hosni Mubarak was toppled in 2011.
His successor Mohamed Morsy ordered the security forces almost a year ago to bring the well-armed militant groups to heel following a deadly assault on a border post by Islamist gunmen. The new hostage crisis poses a fresh challenge to his government as it struggles with an economic crisis and political unrest.
Army and police forces set up new roadblocks and reinforced existing ones in a zone running from the northern Sinai town of Sheikh Zuwayed towards al-Jura further south, trying to choke off supplies and reinforcements for the kidnappers, the source said.
Witnesses saw a military aircraft flying over a convoy of armoured personnel carriers in the area.
The state-run Al-Ahram newspaper said the security forces were moving to surround the kidnappers and quoted a military source as saying a military solution would be the last option.
Morsy had said on Monday there would be no talks with "criminals" and vowed not to submit to blackmail.
The kidnappers are demanding the release of jailed Islamists.
The incident has outraged an already disgruntled police force – officers have blocked a land crossing with the Gaza Strip for five days and temporarily closed off a commercial crossing with Israel in protest at the kidnapping.
Armed groups that espouse a more radical brand of Islam than Morsy's Muslim Brotherhood have exploited a security vacuum in Sinai to launch a series of attacks on Israel and Egyptian security forces.
Cairo's 1979 peace treaty with Israel limits the number of troops it can deploy in Sinai, but Israel agreed to Egypt's request to send in more troops as security unraveled there in 2011. Israel has not commented on the new deployment.
The thinly populated desert region has a string of international tourist resorts along its southern Red Sea coast.