for a deadly attack at a Saudi mosque. Saudi officials say the suicide bombing in the southern city of Abha killed 15 people.The Hijaz Province of the Islamic State said it carried out the attack. It made the claim in a Twitter statement hours after the attack. Abha is close to Saudi Arabia's border with Yemen.The group vowed to launch more strikes against "tyrants in the Arabian peninsula...in the coming days."The Croatian government said it is "doing all it can" in connection with a death threat against a Croatian hostage. Islamic State militants released a video in which they threatened to execute the man.In the video, the hostage identified himself as Tomislav Salopek. He said he would be killed if Egypt's government did not release Muslim women held in prisons.Wednesday night, Croatia's government released a statement. It said it was "doing all it can to promptly resolve the difficult situation." It did not give any details.Croatian Foreign Minister Vesna Pusic left for Cairo Thursday. Officials say he was in contact with Egyptian officials.Mr. Salopek said in the video that he was kidnapped July 22.Chinese relatives of passengers on the missing Malaysian flight MH370 have criticized the recent announcement about the mystery. On Wednesday, Malaysian Prime Minister Najib Razak confirmed that a wing piece found on an Indian Ocean island was part of the missing plane.Several Chinese family members say the announcement only increased their frustration as investigators had not given confirmation.Malaysia's prime minister had said an international team of experts had "conclusively confirmed" that the piece belonged to the missing plane. However, investigators in France only called it a "very strong presumption" that the piece belonged to MH370.Chinese family members say that both French investigators and Boeing – the maker of the aircraft – should confirm the report.