Multiple explosions rocked Venezuela’s capital Caracas early on Saturday and columns of black smoke and aircraft could be seen, according to Reuters witnesses and images circulating on social media.

A power outage affected the southern area of the city, near a major military base, witnesses said.

It was not immediately clear what caused the disturbances, which began about 2 a.m. (0600 GMT), or exactly where they were occurring. Reuters could not immediately verify the social media videos.

U.S. President Donald Trump has repeatedly promised land operations in Venezuela. He has not publicly detailed his aims but has privately pressured President Nicolas Maduro to flee the nation, Reuters has reported. Trump said on Monday it would be “smart” for Maduro to leave power.

The Pentagon referred questions to the White House, which declined to comment.