The officials said Thursday the militants ordered the soldiers off a bus as they returned from leave to rejoin their units. The officials say the soldiers were killed execution style.

The officials, who spoke on condition of anonymity because they were not authorized to speak to media, said the incident happened Wednesday in southern Yemen.

The killings are the latest evidence of the growing strength of Islamic militants in parts of Yemen, which has been rocked by an uprising against the authoritarian regime of President Ali Abdullah Saleh.