NASHVILLE, Tenn. -- Country music stars and fans joined together to urge prayers for Randy Travis overnight as he recovered from brain surgery following a stroke at a Texas hospital.

Travis remained in critical condition after surgery Wednesday night to relieve pressure on his brain, publicist Kirt Webster said. The 54-year-old Grammy Award-winning singer had been improving while being treated for heart failure caused by a viral infection when he had the stroke.

Steady concern for Travis, a popular and pivotal figure in country music, turned to active support as stars like Hillary Scott of Lady Antebellum and Martina McBride and the Grand Ole Opry used Twitter to join Webster's call for prayers. Hundreds of users reached out using the hashtag PrayforRandy.

"We're all pulling for you Randy," Brad Paisley said via Twitter.

The setback occurred hours after doctors said Travis was showing signs of improvement since the start of treatment Sunday for congestive heart failure.

It was not clear what kind of stroke Travis suffered. The most common type of stroke is caused by a blood clot that travels to the brain. The other kind happens when a blood vessel in the head bursts or leaks. Stroke patients who get treatment quickly are usually given a drug to dissolve the clot that caused the stroke.

Drs. William Gray and Michael Mack of the Baylor Health Care System in Texas described Travis' condition and hospitalization in a video statement earlier Wednesday.

"His condition has stabilized, and he has shown signs of improvement," Mack said in the video. "On behalf of Mr. Travis' family, friends and associates, we would like to express our extreme gratitude for the overwhelming affection and support that Mr. Travis has received."

The "Three Wooden Crosses" singer was in good health until three weeks before he was hospitalized, when he contracted a viral upper respiratory infection, Gray said.

The viral illness led to a weakened heart muscle that eventually worsened into heart failure.

Travis was admitted to Baylor Medical Center McKinney near his home in Tioga, about 60 miles north of Dallas, through the emergency room Sunday. The singer underwent a procedure to have a pump inserted by catheter that helps increase blood flow before being transferred to The Heart Hospital Baylor Plano.

Travis' illness comes as he's been trying to put his life back together following a series of embarrassing public incidents involving alcohol. Travis pleaded guilty to driving while intoxicated in January following an arrest last year and received two years of probation and a $2,000 fine. He was required to spend at least 30 days at an alcohol treatment facility and complete 100 hours of community service.

He recently made several public appearances, including a spot on the Country Music Association Festival's nightly concert lineup and a poignant performance at George Jones' funeral.

Webster said from the hospital Travis' fiancee Mary Beougher was at his side and that he is surrounded by family and friends, including his brother, Dennis Traywick, and his pastor, Jeff Perry. Kenny Rogers, the Oak Ridge Boys, Chuck Norris and several others have called to check in on Travis.

The North Carolina-born Travis is a traditional country purist known for hits "Forever and Ever, Amen" and "I Told You So." His 1986 Warner Bros. debut album "Storms of Life" sold 4 million copies, and helped return country music to the sound of Hank Williams and George Jones.

"I always feel like he's part of our family, he's in our family," Keith Urban said in an interview Wednesday morning in Nashville. "And I was one of those guys in Australia that bought 'Storms of Life' and became a Randy fan very quickly in late '80s, and I really feel for him right now."

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Associated Press writer Kristin M. Hall contributed to this report in Nashville, Tenn.