CARACAS -- Venezuela on Saturday denounced a "military aggression" by the United States, after large explosions were heard and aircraft were seen over the capital Caracas earlier in the day.

The Venezuelan government said that the military strike targeted civilian and military sites in at least four states of the country, including Caracas, as well as the states of Miranda, Aragua and La Guaira, adding that the US action blatantly violated the UN Charter.

Low-flying aircraft were spotted, and clouds of smoke were seen following loud explosion sounds at around 2:00 am (0600 GMT) Saturday in Caracas.

Reports said brief power outages occurred in some areas, including a military base in Caracas.

In the statement, the Venezuelan government said that President Nicolas Maduro had "ordered all national defense plans to be implemented" and declared "a state of external disturbance."

Shortly after the attack started, CBS White House reporter Jennifer Jacobs cited US officials saying that President Donald Trump had ordered the strikes, while FOX News reported that US officials confirmed the bombings.

Colombian President Gustavo Petro on Saturday called for an urgent meeting of the Organization of American States and the UN on the attack in Venezuela.

Over the past months, the United States has maintained a significant military presence in the Caribbean, including the USS Gerald R. Ford, an aircraft carrier, and about 15,000 troops, much of it off Venezuela's coast, purportedly to combat drug trafficking — a claim Venezuela has denounced as a thinly veiled attempt to bring about regime change in Caracas.