CAIRO (AP) -- A deadly suicide bombing that hit a bus of South Korean Christians visiting Biblical sites in Egypt and Israel has raised fears that Islamic militants battling security forces in the Sinai Peninsula are turning to target foreign tourists, a potential new blow to a struggling industry vital to Egypt's economy.
Though it has proven resilient to past attacks, Egypt's slumping tourism is already suffering from three years of political turmoil that has scared away visitors. After hopes of a rebound, last year saw the fewest visitors yet since the 2011 uprising that toppled autocrat Hosni Mubarak.
The new attack could be even more damaging because it threatens a region that has kept Egypt's tourism alive even during the downturn -- the beach resorts of the Red Sea in the Sinai Peninsula. Those resorts on Sinai's eastern and southern coasts, a favorite of divers and Europeans escaping the winter, had seemed a world away from the political unrest in the Nile Valley, and even from the wave of Islamic militant violence on Sinai's northern Mediterranean coast.
Militants have waged a campaign of bombings and shootings targeting the military and police forces since the army ousted Islamist President Mohammed Morsi last summer. Their nascent insurgency began in northern Sinai, but has struck with increasing frequency in the capital Cairo and other cities.
There was no immediate claim of responsibility for Sunday's bombing of the bus in Taba, a Red Sea resort on the border with Israel. But suicide bombings have become a hallmark of the al-Qaida-inspired militant groups operating elsewhere.
The bus, carrying more than 30 South Korean Christians, their Egyptian guide and an Egyptian driver was waiting to cross into Israel, the next stage in a tour of Biblical sites that took them earlier to Sinai's ancient Saint Catherine's Monastery.
The driver and two South Koreans got out of the bus and checked the cargo hold. As they were reboarding, the suicide bomber pushed through the open door into the bus and detonated his explosives, Interior Ministry spokesman Hani Abdel-Latif said.
The blast tore apart the yellow tour bus, killing the driver and three South Koreans and wounding at least a dozen more tourists, Egyptian security officials said. The officials spoke on condition of anonymity because they were not authorized to talk to the press.
The hit comes as Egypt's tourism industry is trying to bounce back. In 2010, the sector was one of the most powerful engines of the country's economy, bringing in more than 14.7 million tourists and some $12 billion in revenue. It employed around 13 percent of the workforce and raked in a fifth of Egypt's foreign currency.
The 2011 revolt against Mubarak, and the ensuing instability hit it hard: That year, visitors dropped to 9.6 million, earning the country $8.8 billion. In 2012, the industry slowly clawed back, with around 10.5 million tourists coming.
Last year, however, saw the ouster of Morsi and escalating violence as authorities cracked down on his Muslim Brotherhood, and visitors dropped to 9.5 million, fewer even than 2011. The large majority of those tourists -- nearly three-quarters of them -- stuck to the Red Sea resorts.
Still, even south Sinai has felt the blow. In Sharm el-Sheikh, Sinai's main Red Sea resort, about 100 miles (160 kilometers) south of Taba, occupancy at the city's hotels is currently averaging around 45 percent, but most guests are Egyptians enjoying vastly discounted rates, according to tourism workers.
Adel Shokry, manager of a luxury hotel there, sought to play down the likely impact of Sunday's bombing, arguing that past attacks have had short-lived impact on tourism in Sharm.
"I believe the attack will not gravely affect tourism ... and things will go back to normal," said Shokry.
It is not immediately known if Sunday's attack marks the start of a militant campaign against tourism. Egypt's militants targeted tourists in the 1990s, trying to cripple the economy as they waged an insurgency to topple Mubarak's government. Security forces ruthlessly crushed the campaign by the end of the decade.
The last major attacks on tourists came in a string of militant bombings against resorts in southern Sinai -- including in Taba -- between 2004 and 2006, killing about 120 people. But the tourism industry quickly rebounded.
This time, however, the industry is already deeply weakened, particularly in the Nile Valley, which was the traditional attraction for tourists with its wealth of pharaonic antiquities.
Cairo, home to the Giza Pyramids and Sphinx and the famed Egyptian Museum, sees few visitors. The past three years have seen repeated eruptions of violence. Since Morsi's ouster, nearly daily protests by his supporters often turn into clashes with police.