Spain condemned what it called a violation of international law in Venezuela, Prime Minister Pedro Sanchez wrote in a letter sent to members of his Socialist Party on Sunday after US President Donald Trump’s raid to capture Nicolas Maduro.

His comments went further than his remarks on Saturday, in which he said he would not recognise the intervention.

The Socialists’ hard-left coalition partner Sumar had urged the government to condemn the US strikes that resulted in the Venezuelan president’s capture, with party sources describing it as an act of imperialist piracy against a member state of the United Nations.

Sanchez’s letter described the “violation of international law in Venezuela, an act that we strongly condemn”.

Trump says Maduro masterminded the flow of drugs into the US and was illegitimately in power due to vote-rigging. Maduro denies those claims, and officials in Caracas have demanded his release.

Spain is home to the largest Venezuelan migrant population outside Latin America and the US, and they include senior opposition figures such as Edmundo Gonzalez and Leopoldo Lopez.

On Sunday, hundreds of left-wing protesters demonstrated at the US embassy in Madrid to oppose Washington’s actions after thousands of opposition activists and others gathered at Madrid’s Puerta del Sol on Saturday to celebrate Maduro’s detention.

The question of the legality of the US action is likely to be the subject of much debate. International law prohibits the use of force in international relations except for narrow exceptions such as authorisation by the UN Security Council or in self-defence.

The UN Security Council is due to meet on Monday.