Jihadist group Ansar Beit al-Maqdis on Tuesday claimed the suicide bombing in Egypt of a tour bus that killed three South Koreans and their local driver.
The bombing on Sunday, near the Taba border crossing with Israel, was the first targeting tourists since the military overthrow of Islamist president Mohamed Morsi in July sparked a militant campaign that has killed scores of police and soldiers.
"One of the heroes of Ansar Beit al-Maqdis carried out the attack on a tourist bus heading towards the Zionist entity (Israel)," said a statement attributed to the group and posted on jihadist forums.
It added that the suicide attack was "part of our economic war against this regime of traitors ... which kills the innocent, destroys houses, ransacks properties and lays waste to land on the border with the Zionist enemy".
The group warned Egypt's government of new attacks aimed at its "economic interests everywhere to force it to stop its actions against Muslims".
The tourists were all members of the same church group from the central South Korean county of Jincheon, and were on a 12-day trip through Turkey, Egypt and Israel.
They had been about to cross into Israel when the blast occurred.
Fourteen South Koreans were also wounded in the bombing and were receiving treatment at a hospital in the popular Sinai resort of Sharm el-Sheikh.
Two Egyptians were also wounded in the blast.
The head of Egypt's Chamber of Tourism said the attack could have been aimed at hitting the tourism industry, one of Egypt's top revenue generators.
"The attack aimed at harming tourism in general," said Elhami al-Zayat.
The Sinai-based Ansar Beit al-Maqdis (Partisans of Jerusalem) has claimed responsibility for several high-profile attacks, including a car bombing at police headquarters in Cairo and the shooting down of a military helicopter.
The Al-Qaeda-inspired group also tried but failed to assassinate interior minister Mohamed Ibrahim last year.
The military has sent tanks and troops to combat the militants in the Sinai, amid fears the group is now changing its tactics.
"A continuation in attacks on tourists would mean a shift in strategy by jihadist groups that until now targeted the military and police," said Issandr El Amrani of the International Crisis Group.
"But that cannot be judged after one attack," he added.
Islamist militants have killed dozens of tourists in sporadic attacks over the past several decades, most recently in a 2009 bombing that killed a French tourist in Cairo.
Police under now deposed president Hosni Mubarak had all but stamped out Islamist militancy after a spate of Sinai resort bombings between 2004 and 2006.
But the three-year period of unrest after Mubarak's overthrow in 2011 has allowed the militants to regroup in the restive Sinai peninsula and to branch out to the Nile Delta.