"The arbitrary detention by the US of vessels from other countries in international waters is a serious violation of international law," Mao told a briefing, commenting on the US’s detention of the Marinera oil tanker.
China opposes any actions that violate the sovereignty and security of other countries, the spokeswoman said.
"China consistently opposes illegal unilateral sanctions that have no basis in international law and are not authorized by the UN Security Council, as well as any actions that violate the fundamental purposes and principles of the UN Charter and infringe upon the sovereignty and security of other countries," Mao added.