U.S. President Donald Trump, who is being treated for COVID-19 at a military hospital, went for a short drive to wave at supporters on Sunday.

According to the Associated Press and other foreign media, Trump briefly left Walter Reed National Medical Center for a drive-by in front of crowds of supporters lining the street outside. 

Trump, wearing a mask, was seen in the back of a slow-moving SUV, waving to the assembled crowds. 

In a video post on social media, Trump said it’s been a "very interesting journey and he learned a lot about COVID.” He added that he gets it and understands it.

However, his surprise move drew sharp criticism from health experts and media. 

The Hill, a Washington-based political newspaper, said that the drive-by triggered immediate safety concerns and outrage as the president, who is infected with a highly contagious disease, was with two Secret Service agents in the vehicle, putting them in danger.