"As soon as we heard about this accord, we began consultations with Sao Tome authorities," Portugal's Foreign Minister Paulo Rangel said in a late Thursday interview with television station SIC Noticias.

"First Portugal, and other European countries have expressed surprise, apprehension and perplexity about this accord", he said, while recognising that Sao Tome is an "independent and sovereign" state.

But "given that we are in an international situation where the Russian federation is responsible for a war of aggression which involves the European continent, we have evidently expressed our great concern."

According to Russia's official news gazette, Sao Tome and Russia signed an agreement on April 24 in Saint Petersburg that calls for military training, logistical support, and "possible collaborations" involving Russian ships and planes.

These developments come as the president of Guinea-Bissau, another former Portuguese colony in Africa, was in Russia to attend commemorations for the end of World war II.

Several African countries, including Mali, Niger and Burkina Faso, have recently ended defence agreements with France and signed accords with Moscow.