A suicide bomber blew himself up near Egypt’s ancient Karnak temple in the southern city of Luxor on Wednesday, security sources and witnesses said, the second attack in just over one week targeting Egypt’s vital tourism industry.

No group immediately claimed responsibility for the attack in which four Egyptians were wounded, the health ministry said.

Islamist militants have killed hundreds of police and soldiers over the past two years in a campaign to topple the Egyptian government, but there have recently been attacks on softer tourist and economic targets.

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Gunmen on a motorcycle shot dead two members of Egypt’s tourism and antiquities police force on a road near the Giza pyramids last week.

The Interior Ministry said in a statement it had “foiled a terrorist attack” at Karnak and that two assailants had been killed and a third wounded. It did not give further details.

Security sources said the casualties at Karnak included bazaar shop owners and two policemen. No tourists were wounded, according to government officials.

Images from the scene of the explosion showed uniformed and plainclothes police gathered nearby, and ambulances parked beside tourist buses.

Antiquities Minister Mamdouh al-Damaty said he had, in coordination with the Interior Ministry, ordered security to be bolstered at ancient sites across Egypt.

Tourism is one of the top sources of income and foreign currency earnings for the Arab world’s most populous country, and the sector has made an effective target for militants.

In 1997, 58 tourists and four Egyptians were killed in an attack in Luxor at a woman pharaoh’s temple. It took Hosni Mubarak, the veteran autocrat ousted in a 2011 uprising, several years to crush an Islamist insurgency in the 1990s.

Story by Reuters