Media reports in the Cape Verde islands off West Africa say police there have found eight dead soldiers and three dead civilians at a military barracks.
The website of local newspaper A Semana says two of the dead civilians are Spaniards. All the dead were reportedly shot Tuesday.
The online service of Expresso das Ilhas said the government placed security forces on red alert at the international airport in Praia, the capital, and at the island's ports after the apparent attack.
Media said the barracks housed soldiers protecting a communications hub and that the civilians were working on repairs.
Government officials in the former Portuguese colony were reportedly planning a news conference later in the day after an emergency meeting of the Cabinet.