US President Donald Trump says he will direct US agencies, including the defence department, to "begin the process of identifying and releasing" government files on aliens and extraterrestrial life.

Trump made the declaration in a post on Truth Social, after he accused Barack Obama earlier in the day of revealing classified information when the former president said "aliens are real" on a podcast last week.

"He's not supposed to be doing that," Trump told reporters aboard Air Force One, adding: "He made a big mistake."

Asked if he also thinks aliens are real, Trump answered: "Well, I don't know if they're real or not."

Former US President Obama told podcast host Brian Tyler Cohen that he thinks aliens are real in an interview released last Saturday.

"They're real, but I haven't seen them, and they're not being kept in Area 51," Obama said.

"There's no underground facility unless there's this enormous conspiracy and they hid it from the president of the United States."

After the comment made headlines, Obama sought to clarify he thinks it is statistically likely life exists beyond Earth, given the vastness of the universe.

In a follow-up post on Instagram, Obama, who served as US president between 2009-17, clarified: "I saw no evidence during my presidency that extraterrestrials have made contact with us. Really!"

Obama's initial comments were made during a quickfire "lightning" round of questions on the podcast.

There was no indication that Obama relied on classified information when he gave the interview. The BBC has contacted Obama for comment. The Democrat and Trump, a Republican, are longstanding mutual political antagonists.

For his part, Trump said on Thursday on Air Force One that while a lot of people believe in the existence of aliens, he never talks about it, and "doesn't have an opinion on it".

Then a few hours later, he posted on Truth Social that "based on the tremendous interest shown" he will seek the release of files "related to alien and extraterrestrial life, unidentified aerial phenomena (UAP), and unidentified flying objects (UFOs), and any and all other information connected to these highly complex, but extremely interesting and important, matters".

The US has seen renewed public interest in UFOs and extraterrestrial life in recent years, sparked in 2017 by reports about a secret Pentagon programme to probe testimony from pilots and other US military members who had reported seeing strange objects in the sky.

In 2022, Congress held the first hearings on UFOs in 50 years and the Pentagon promised more transparency on the matter - setting up a dedicated office to collect reports of all military UFO encounters.

The following year, a US House of Representatives panel on the topic produced no major bombshells nor confirmation of alien life. In a 2024 report, the Pentagon said there was "no evidence" that the US government had encountered alien life, and that most UFO sightings were just ordinary objects.