CAIRO (AP) — An Egyptian security official says gunmen have opened fire on a police vehicle, killing one officer and injuring three others.

Maj. Gen. Nasser el-Eid, Security Director of Fayoum governorate, says the militants fired from a distance at the police vehicle carrying prisoners along the road between Cairo and Fayoum on Saturday.

Officials rushed the injured men to a hospital and the prosecutor has opened an investigation.

No group immediately claimed responsibility for the attack.

Egypt faces increasingly sophisticated attacks from militant organizations, including an affiliate of the Islamic State group.

Police searches and diplomatic efforts have intensified over the fate of a Croatian hostage held in Egypt by Islamic State extremists, who threatened to kill him if the government did not release imprisoned Islamist women.