The US says it has seized two oil tankers linked to Venezuela for violating economic sanctions. 

US forces boarded the first tanker in the North Atlantic, near Iceland, after pursuing it for weeks. The ship was registered as a Russian vessel. Moscow has denounced the seizure as a violation of international law. The second vessel was seized in the Caribbean Sea.

According to US officials, both ships are part of a "shadow fleet" that carries oil from Russia, Iran and Venezuela in defiance of Western sanctions.