Barack Obama has called for "concrete steps" to tackle mass shootings after a gunman massacred at least 26 worshipers and wounded 20 others at church in Texas.

Offering his condolences, the former US President tweeted: "We grieve with all the families in Sutherland Springs harmed by this act of hatred, and we’ll stand with the survivors as they recover."

In a call for action, he added: "May God also grant all of us the wisdom to ask what concrete steps we can take to reduce the violence and weaponry in our midst."

In contrast, Donald Trump said the attack was due to a "mental health problem" and wasn't "a guns situation."

When asked what policies he might support in response to the shooting at a press conference in Tokyo, the US President said that based on preliminary reports, the gunman was "a very deranged individual, a lot of problems."

Texas church shooting: What we know so far

"We have a lot of mental health problems in our country, as do other countries. But this isn't a guns situation," he said.

"Fortunately somebody else had a gun that was shooting in the opposite direction.

"This is a mental health problem at the highest level," he added. "It's a very, very sad event."

Texas church shooting Show all 9 1 /9 Texas church shooting Texas church shooting The site of the mass shooting at First Baptist Church in Sutherland Springs, Texas Reuters Texas church shooting First responders are at the scene of shooting at the First Baptist Church Reuters Texas church shooting Enrique and Gabby Garcia watch investigators at the scene of the mass shooting AP Texas church shooting Law enforcement officials investigate the scene at the First Baptist Church in Sutherland Springs, Texas Reuters Texas church shooting Carrie Matula embraces a woman after a fatal shooting at the First Baptist Church in Sutherland Springs Associated Press Texas church shooting Law enforcement officials gather near the First Baptist Church Getty Images Texas church shooting Community members come together for a candlelight vigil for the victims of the deadly church shooting in Sutherland Springs Laura Skelding/AP Texas church shooting Mourners participate in the candlelight vigil held for the victims Jay Janner/Austin American-Statesman via AP Texas church shooting A vehicle is hauled onto a flatbed truck where the suspect in a deadly church shooting was found dead in Guadalupe County William Luther/Austin American-Statesman via AP

The lone gunman, identified in US media as Devin Patrick Kelley, opened fire with an AR-15 assault rifle after entering the Sutherland Springs First Baptist Church, killing worshippers ranging in age from five to 72.

Kelley was fired upon and chased by a local resident and fled in his vehicle.

He was later found dead in a neighbouring county.