U.S. Secretary of Defense Lloyd Austin was taken to a Washington, D.C. hospital on Sunday for treatment of "symptoms suggesting an emergent bladder issue", a Pentagon spokesman said.

Austin, 70, was retaining his duties during his hospitalization, Pentagon Press Secretary Maj. Gen. Pat Ryder said in a written statement.

Austin was criticized last month for failing to disclose a cancer diagnosis and subsequent hospitalizations in December and January, including to President Joe Biden. He apologized during a televised news briefing.

White House National Security spokesman John Kirby on Sunday said U.S. Defense Secretary Lloyd Austin's doctors think he may need additional care.

"We'll see, you know, when he can be released, but obviously they still feel like he may need some additional care. ... Part of that is just physical therapy," Kirby told CBS's "Face the Nation."

Kirby said "there is routine regular communication" between President Joe Biden and Austin and that the secretary remains "actively involved and engaged" from the hospital.

The Pentagon did not tell President Joe Biden and other top officials about Defense Secretary Lloyd Austin’s hospitalization for three days, three U.S. officials said.

National security adviser Jake Sullivan and other senior White House aides didn’t know of Austin’s Jan. 1 hospitalization until the Defense Department sent over word Jan. 4, two other U.S. officials said. Sullivan informed Biden shortly after DOD’s Thursday notification.

U.S. Sen. Tom Cotton, R-Arkansas, said Secretary of Defense Lloyd Austin needs to explain why the White House and senior officials weren't immediately notified that he'd been hospitalized earlier this week until days later, amid a complex time as the Biden administration deals with a slew of national security matters abroad. 

Two dozen Republican lawmakers are demanding answers from the Pentagon after Walter Reed National Military Medical Center sent a "cease and desist" letter to Catholic priests to stop providing care during Holy Week, slamming the move as a violation of the First Amendment.

24 Republican members of Congress penned a letter to Defense Secretary Lloyd Austin. In the letter, obtained exclusively by Fox News Digital, the lawmakers blast the Biden administration’s "attack on the Christian faith." 

Sen. John Fetterman checked himself into the Walter Reed National Military Medical Center on Wednesday night to receive inpatient care for clinical depression, his chief of staff Adam Jentleson said Thursday.

The first-term Democratic senator has experienced depression throughout his life, but “it only became severe in recent weeks,” Jentleson said in a statement.

“After examining John, the doctors at Walter Reed told us that John is getting the care he needs, and will soon be back to himself.”

Sen. John Fetterman (D-PA) checked himself into Walter Reed Hospital to receive treatment for clinical depression on Wednesday night, his office announced.

“Last night, Senator John Fetterman checked himself into Walter Reed National Military Medical Center to receive treatment for clinical depression. While John has experienced depression off and on throughout his life, it only became severe in recent weeks," chief of staff Adam Jentleson said in a statement.

Sen. John Fetterman has checked himself into a Washington hospital for treatment of clinical depression, his office announced Thursday, another setback after a hospitalization last week for light-headedness and after a stroke he suffered during last year’s campaign.

“While John has experienced depression off and on throughout his life, it only became severe in recent weeks,” his chief of staff, Adam Jentleson, said in a statement.

US President Donald Trump has left hospital, three days after being admitted with Covid-19, vowing to be back on the campaign trail soon.

He flew for the short trip back to the White House on the presidential helicopter Marine One.

"Feeling really good!" Mr Trump tweeted earlier. "Don't be afraid of Covid. Don't let it dominate your life."

More than 7.4 million cases of Covid-19 have been recorded in the US. The virus has killed nearly 210,000 Americans.

President Trump has returned to the White House on Monday, on his fourth day at Walter Reed National Military Medical Center, though his doctor said he might not be "out of the woods" yet.

The president walked from Marine One into the White House residence, and up to the balcony, where he removed his mask.

The president announced his expected departure from the military hospital earlier with a tweet. "Don't be afraid of COVID," he wrote. "Don't let it dominate your life."