A Venezuelan official says the country is banning sea trips to and from three Dutch Caribbean islands — a region that has been linked to efforts to undermine President Nicolas Maduro by sending aid to the South American nation.

Falcon state Civil Protection Director Gregorio Jose Montano said Tuesday that the indefinite shutdown of the "maritime border" affects Curacao, Aruba and Bonaire.

It comes as opposition leader Juan Guaido rallying international support for his challenge to Maduro.

Guaido has called for international emergency aid for Venezuela, including from Curacao, about 40 miles (65 kilometers) from Venezuela.

Maduro vows to block the aid, saying it's part of a U.S. coup.

Dutch officials have said they're opening Curacao as a hub for emergency shipments.