A gunman entered a small church in southeast Texas and opened fire, killing at least 26 worshippers and wounding many others in the latest mass shooting to plague the United States, according to authorities and media reports.

The shooting occurred at the First Baptist Church in Sutherland Springs in Wilson County, about 40 miles (65 km) east of San Antonio. The suspect fled the scene in a vehicle but was killed about 12 miles away in neighbouring Guadalupe County, according to local media and Sergeant Robert Murphy, a spokesman for the Guadalupe County Sheriff's Office said.

The suspect has been identified as 26-year-old Devin Patrick Kelley from New Braunfels, Texas. Kelley served in the U.S. Air Force from 2010 to 2014, and was court-martialed in May 2014.

The suspect's motive has not been disclosed by authorities. But law enforcement officials who were not identified have said the gunman as a white, 26-year-old man, the New York Times and other media reported.

Wilson County Sheriff Joe Tackitt told CNN that at least 20 people were killed. Texas Lieutenant Governor Dan Patrick told Fox News that at least 25 people were killed and 30 injured.

The 14-year-old daughter of pastor Frank Pomeroy was killed, the family told several television stations.

Jeff Forrest, a 36-year-old military veteran who lives a block away from the church, said what sounded like high-caliber, semi-automatic gunfire triggered memories of his four combat deployments with the Marine Corps.

'I was on the porch, I heard 10 rounds go off and then my ears just started ringing," Forrest said. "I hit the deck and I just lay there.'

The massacre comes just weeks after a sniper killed 58 people at an outdoor concert in Las Vegas, the deadliest mass shooting in modern US history. The shootings have stirred a years-long national debate over whether easy access to firearms was contributing to the trend.

President Donald Trump said he was monitoring the situation while in Japan on a 12-day Asian trip.

'May God be w/ the people of Sutherland Springs, Texas. The FBI & law enforcement are on the scene,' he said on Twitter.

According to the witnesses, about 20 shots rang out at 11:30 a.m. (1730 GMT) during the church services, according to media reports. It was unclear how many worshippers were inside at the time.

After the shooting, the suspect sped away in a car and was soon cornered by sheriff's deputies just outside of Wilson County in Guadalupe County, Wiley told Reuters. He did not know if the shooter died of a self-inflicted gunshot or was killed by deputies.

Connally Memorial Medical Center in Floresville received eight patients, the hospital said in a statement, while Brooke Army Medical Center at Fort Sam Houston received another eight.

At Connally, three people were treated and released, one is in critical condition and four were transferred to the University Hospital in San Antonio for a higher level of care.

The First Baptist Church is one of two houses of worship in Sutherland Springs, an area that is home to fewer than 900 residents, according the 2010 Census. There are also two gas stations and a Dollar General store in town.

The white-painted, one-story structure features a small steeple and a single front door. On Sunday, the Lone Star flag of Texas was flying alongside the US flag and a third, unidentified banner.

Inside there is a small raised platform on which members sang worship songs to guitar music and the pastor delivered a weekly sermon, according to videos posted on YouTube. In one of the clips, a few dozen people, including young children, can be seen sitting in the wooden pews.

Pastor Paul Buford of River Oaks Church, about 2 miles from First Baptist, said the community was deeply shaken.

'We are holding up as well as we can,' he said. 'We are a strong community.'

The shooting occurred on the eighth anniversary of the Nov. 5, 2009 massacre of 13 people at the Fort Hood Army base in central Texas. A US Army Medical Corps psychiatrist convicted of the killings is now awaiting execution.

In 2015, a white gunman killed nine black parishioners at Emanuel African Methodist Episcopal Church in Charleston, South Carolina. The gunman was sentenced to death for the racially motivated attack.

In September, a gunman killed a woman in the parking lot of a Tennessee church on Sunday morning and wounded six worshippers inside the building before shooting himself in a scuffle with an usher who rushed to stop the attack.