Islamic Group Appears to Aim at Cairo’s Heart : Terrorism: A homemade bomb in a crowded coffee shop comes in wake of attacks on tourist industry.

CAIRO —  Islamic extremists appeared to claim responsibility Saturday for a homemade bomb that ripped through a crowded coffee shop, signaling a turning point by directing the fundamentalists’ war on foreign tourism into the heart of downtown Cairo.

The explosion, which killed two foreigners and two Egyptians and wounded 15 others, is the most violent so far of more than a dozen terrorist attacks that have killed five foreigners and wounded two dozen more since Islamic militants targeted Egypt’s $3-billion-a-year tourist industry last year.

Those injured in Friday night’s blast were two Americans, a Canadian, three Somalis and a Frenchman, in addition to eight Egyptians, hospital officials said. The U.S. Embassy said the Americans, identified as Jill Papio and Mathew Chipico, were only slightly injured and remained in the hospital’s intensive care unit for observation.

Killed in the attack were two Egyptians, a Turk and a Swede, hospital officials said.

The homemade bomb, fashioned of TNT and nails packed into a bottle, exploded in a crowded cafe in the middle of Cairo’s Tahrir Square, the center of the city and the location of the Egyptian Museum, the Arab League, the Foreign Ministry, the Hilton and Cleopatra hotels and a number of airline, travel and tourist shops and offices.

An unidentified man known as a spokesman for the Gamaa al Islamiya, an underground militant organization seeking to establish an Islamic state in Egypt, told reporters in the southern Egyptian city of Asyut that Islamic militants had carried out the bombing as part of the group’s “vendetta with the government.”

“Tourism is not the goal but is a means to pressure the regime into releasing members of the Gamaa al Islamiya who were unjustly arrested,” said the man, speaking to journalists at a mosque on Saturday afternoon.

But several hours later, the Islamic organization in a faxed statement to an international news organization denied any responsibility for the attack.

“With regard to the explosion which occurred on Friday in a coffee shop in Tahrir Square and in view of the attempt of the Egyptian police to attribute the incident to the Gamaa al Islamiya, the Gamaa denies that it has any connection with the incident, whether near or far,” the statement said.

On Saturday, crowds of onlookers thronged around the battered shell of the coffee shop, where broken tables and chairs, shards of glass and the odd teacup and spoon had been swept into piles and black-uniformed police officers stood guard.

Witnesses said the blast occurred during what is the peak evening hour in the Muslim holy fasting month of Ramadan, when Egyptians gather in public parks and coffee shops after breaking the daylong fast at sunset.

The bomb apparently was wrapped in a leather bag or jacket and placed under a table in the crowded Wadi al Nil coffee shop, police said. They said one of the dead Egyptians, identified as Emad Abdel-Baset, may have been involved in the bombing.

The repeated attacks on foreign tourists have prompted large-scale cancellations, driving tourist bookings down an estimated 20% over the past few months and costing Egypt hundreds of millions of dollars in lost revenues.

But attacks so far have generally been carried out using automatic weapons or small firebombs to target tour buses or Nile cruise boats, mostly in the southern Egyptian areas of Dairut, Asyut and Minya. While two tour buses have been attacked near the Pyramids on the outskirts of Cairo, the coffee shop bombing represents the first recent terrorist incident in the heart of Cairo and is the first time in which so large an explosive device has been used.