A Venezuelan navy coastal patrol boat sank in the Caribbean after allegedly ramming a cruise ship that it had ordered to change direction.
The owners of the Portuguese-flagged RCGS Resolute said the naval vessel Naiguata also fired shots in an "act of aggression in international waters”.
The collision left the cruise ship, which has a reinforced hull for sailing in icy waters, with only minor damage.
Venezuela accused the Resolute of an act of "aggression and piracy".
It also said it "did not rule out" that the cruise ship "was transporting mercenaries to attack military bases in Venezuela".
President Nicolás Maduro has previously accused the United States and other countries of plotting to overthrow him.
The incident took place near La Tortuga Island, a Venezuelan federal dependency, on 30 March.
Columbia Cruise Services, which operates the Resolute, said the cruise ship had been carrying out routine engine maintenance in international waters more than 13 nautical miles (24km) from La Tortuga.
A statement from the Hamburg-based company said that shortly after midnight, the Naiguata radioed the Resolute, questioning its intentions, and ordered the captain to follow it to a port on Isla Margarita, to the east.
"While the master was in contact with the head office, gunshots were fired and, shortly thereafter, the navy vessel approached the starboard side at speed... and purposely collided with the RCGS Resolute," it added.
"The navy vessel continued to ram the starboard bow in an apparent attempt to turn the ship’s head towards Venezuelan territorial waters."
Although the Resolute - a purpose-built polar expedition vessel - suffered minor damage, the patrol boat began taking on water after hitting its bulbous bow, according to the statement.
Columbia Cruise Services said the Resolute remained in the area for more than an hour and contacted rescue co-ordinators on the Dutch Caribbean island of Curaçao. All attempts to contact the Naiguata went unanswered and the Resolute eventually sailed to Willemstad on Curaçao, it added.
A statement by the Venezuelan military (in Spanish) accused the Resolute of "cowardly and criminal" behaviour, "since it did not attend to the rescue of the crew".
It said all the crew of the Naiguata had been rescued, but did not give details.
Defence Minister Vladimir Padrino López accused the Resolute of ramming the vessel, "which caused its sinking".
President Maduro said an investigation had been launched and he expected "maximum collaboration" from authorities in Curaçao.