Opposition National Assembly President Juan Guaido, who declared himself interim president of Venezuela, speaks with the media upon his arrival to National Assembly in Caracas, Venezuela, Tuesday, Jan. 29, 2019. Venezuela’s chief prosecutor on Tuesday asked the country’s top court to ban Guaido from leaving the country, launching a criminal probe into his anti-government activities while international pressure builds against President Nicolas Maduro. (AP Photo/Fernando Llano)

CARACAS — Venezuela’s Supreme Court barred opposition leader Juan Guaido from leaving the country Tuesday, a move certain to heighten tensions as the man challenging President Nicolas Maduro’s claim to the presidency presses forward with establishing a transitional government and the US warns of “serious consequences” if he is harmed.

The government-stacked high court announced the order just hours after chief prosecutor Tarek William Saab announced that he was opening a criminal investigation into Guaido’s anti-government activities and requested that restrictions be placed on his movements abroad. The court also approved Saab’s request that all of Guaido’s financial assets be frozen.

US national security adviser John Bolton issued a warning to the Maduro government earlier in the day urging them not to harm Guaido, the head of the opposition-controlled congress who has been recognized by the Trump administration and two dozen other nations as Venezuela’s rightful president.