Venezuela on Saturday arrested three United States citizens, two Spaniards and a Czech national over their alleged participation in a U.S.-sponsored plot to kill President Nicolás Maduro and several members of his government.

The arrests of the six foreigners  were announced by Interior Minister Diosdado Cabello on state TV on Saturday.

“These groups seek to seize the country’s wealth, and we as a government will respond firmly to any destabilization attempt,” Cabello said, according to a Reuters report. He added that about 400 rifles originating in the United States had been seized.

The U.S. State Department confirmed that three American citizens, including one Navy service member, are being held in Venezuela, but it rejected any links to an assassination attempt. 

During his press conference on Saturday, Cabello argued that the arrested Spanish nationals had links to Spain’s secret service and were planning the killing of a mayor.