Donald Trump has called the massacre at a Texas Baptist church, 'an act of evil'.

Speaking in Japan on the second day of a 12-day Asian tour, the US President said: "You cannot put into words the pain and grief we all feel" for the victims."

"Americans do what we do best, we pull together," he said said at the start of a meeting with business leaders the country's capital Tokyo. "We stand strong, oh so strong."

He added federal authorities would help Texas in the aftermath of the shooting and that all of America was praying to God.

The US leader had earlier tweeted his condolences.

Mr Trump's predecessor Barack Obama meanwhile, called for “concrete steps to reduce violence and weaponry in our midst.”

The mass shooting occurred at the First Baptist Church in Sutherland Springs, about 30 miles from San Antonio, with witness saying that the gunman - who has been identified as Devin Kelley - started shooting.

"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," he said.

He was later "taken down" by authorities, according to Wilson County Sheriff Joe Tackitt who said that at least 20 people had died, with local media saying it amounted to around half the congregation.

Authorities later confirmed that 26 people had been killed.

Megan Posey, a spokeswoman for Connally Memorial Medical Center, which is in Floresville and about 10 miles from the church, said “multiple” victims were being treated for gunshot wounds.