The vessels set sail last Friday from Isla Mujeres in Mexico's southeastern state of Quintana Roo and were due to arrive in Havana on Tuesday or Wednesday this week, the navy said in a statement.

It said that there had been neither "communication nor confirmation of their arrival" in Cuba and that it has alerted naval commanders in the region and its search and rescue stations.

Since last week, activists from several countries have left Mexican ports on vessels loaded with food and other supplies for the communist-led island, which faces a humanitarian crisis in the face of a US-imposed fuel embargo.

The navy did not specify the identities or nationalities of the crew members on the missing boats but said it was maintaining communication with rescue agencies in Poland, France, Cuba and the United States.

The navy is also in contact "with the diplomatic missions of the crew members' countries of origin" to cooperate and exchange information in real time, the statement said.

The navy said it was using aircraft to search the route between Isla Mujeres and Havana.

It appealed to seafarers and maritime authorities in the Caribbean and the Gulf of Mexico to report any information or sightings of the missing vessels to the nearest naval authority.

US President Donald Trump imposed a de facto oil blockade on Cuba in January after the US ouster of Venezuelan leader Nicolas Maduro, whose government had been its principal source Cuba's fuel supplies.