The explosions killed as many as 88 people and wounding more than 100.
Egyptian security officials said four of the attackers traveled into the Red Sea resort town in pickup trucks, hiding their explosives under vegetables.
More than a thousand foreign and Egyptian workers marched through the city on Sunday, chanting against terrorism in English, Arabic, Italian and German.
The protests followed an exodus of shaken Egyptian and Arab tourists who fled the area late Saturday, as rescue workers continued to comb through the rubble.
The attack, Egypt’s deadliest terrorist strike ever, appeared coordinated with two car bombs detonating simultaneously at 1:15 a.m. only 2 miles apart. A third bomb, thought to be hidden in a suitcase, exploded about the same time near a beachside walkway frequented at night, reported the Associated Press.
One blast tore the front off the 176-room Ghazala Gardens hotel in Naamah Bay, the site of most of the resort’s luxury hotels.
“There was a huge ball of smoke that mushroomed up. It was mass hysteria,” Charlie Ives, a London policeman on vacation, told the British Broadcasting Corp.
The blast at Old Market tore through a coffee shop on the side of a minibus lot.
Mustafa Afifi, the governor of southern Sinai, said the official death toll as of this afternoon was 64, and included seven Westerners, 26 Egyptians, and 31 people who were unidentified.
Egyptian police said more than 70 people had been detained by Sunday, though it was not clear if they were suspected of close ties to the bombers or whether it was part of a general roundup, Reuters reported.
Several hours after the bombings an extremist group claimed responsibility on an Islamic Web site. The group, the Abdullah Azzam Brigades of Al-Qaida in Syria and Egypt, also claimed to have carried out a similar series of bombings that killed 34 people last October at and near the resort town of Taba.
Within hours, a second group, which identified itself as the Holy Warriors of Egypt, claimed responsibility in a fax to newspapers and gave the names of five people it identified as the bombers. Neither claim could be verified.
Egyptian Interior Minister Habib al-Adli said it was too early to tell if al-Qaida or other Islamic groups had any connection to the bombings, but that there probably was a link to the attacks in October, Reuters reported. He called Saturday’s attack “an ugly act of terrorism.”
Egyptian President Hosni Mubarak cut short a vacation to the Mediterranean coast and flew to Sharm el-Sheikh. Accompanied by heavy security, he went directly to the scene at the Ghazala Hotel to speak to officials.
The bombings coincided with the anniversary of the overthrow of the Egyptian monarchy by an army revolt in 1952.
The United States, Israel and European and Middle Eastern countries condemned the attacks, and neighboring Jordan said it was immediately tightening security at its tourist sites.
Sharm el-Sheikh, located along the Sinai’s pristine coast and coral reefs, has become a popular tourist destination, drawing European and Israeli visitors. Residents said the resort in recent days had been filled with Israeli Arabs on vacation, according to the Washington Post.
The area also had become a popular venue for official meetings. In February, Israeli Prime Minister Ariel Sharon and Palestinian leader Mahmoud Abbas met there and agreed to a cease-fire.