A woman was killed by two off-duty officers after she entered the megachurch of celebrity pastor Joel Osteen in Houston, Texas, on Sunday and started shooting, police said.

They said a young child with the woman was critically hurt and another man nearby was wounded.

The off-duty officers were working as security at the church.

Houston police chief Troy Finner said the woman entered the church with a long gun and a backpack shortly before 2pm on Sunday, accompanied by a child about four or five years old.

He said the child was in a critical condition in hospital.

The shooting happened between services at the megachurch that is regularly attended by 45,000 people every week, making it the third largest megachurch in the US, according to the Hartford Institute for Religion Research.

Mr Osteen’s televised sermons reach about 100 countries.

Texas governor Greg Abbott said “our hearts are with those impacted by today’s tragic shooting and the entire Lakewood Church community in Houston. Places of worship are sacred”.

“She had a long gun, and it could have been a lot worse,” Mr Finner said at a news conference.

Mr Osteen said the shooting could have been much worse if it had happened during the larger 11am service.

“We’re devastated,” he said, adding that he would pray for the victims and their families.

Witnesses told reporters that they heard multiple gunshots at about the time the church’s Spanish language service was to begin.

Christina Rodriguez, who was inside the church, told Houston television station KTRK that she “started screaming ‘There’s a shooter, there’s a shooter’,” and then she and others ran to a library inside the building, then stood in a stairway before they were told it was safe to leave.

People stood outside the building as authorities evacuated the church.

Officials later said a reunification centre had been set up at a nearby gym for people to find their loved ones.