Yemen ? Shepherds found the mutilated bodies on Monday of two German nurses and a South Korean teacher who were kidnapped while picnicking in an area of Yemen known as a hideout for al-Qaida.

Experts said the killings bore the hallmarks not of local tribesmen but of jihadist militants who had returned home after fighting in conflicts in Afghanistan, Iraq and elsewhere.

The dead women disappeared in the remote northern province of Saada on Friday while on an outing with six other foreigners, including a German doctor, his wife and their three young children. The whereabouts of the six were unknown, the Yemeni government said.

Yemeni authorities announced a state of high alert in the area and were “conducting extensive searches and investigations,” according to a government statement. Besides the German family, a British man was also missing. They all worked for World Wide Services Foundation, a Dutch aid group helping with medical care in the province.