Texas police have charged a 30-year-old man with murder after a police officer was shot dead while he filled up his patrol car.

Harris County sheriff's deputy Darren Goforth, 47, was refuelling his vehicle on Friday night in suburban Houston when a man approached from behind and fired multiple shots.

The suspect continued firing after the officer fell to the ground.

Harris County Sheriff Ron Hickman said the man charged is Shannon J Miles.

Mr Hickman described the attack as a "cold-blooded assassination" and said they were yet to establish a motive for the killing.

Authorities earlier searched a home about a quarter of a mile from the crime scene.

CCTV of the suspect and images of a red or maroon Ford Ranger truck were also released.

In messages on the force's official Twitter account, Harris County Sheriff's Office said: "Deputy Darren Goforth was a 10-year veteran with the Sheriff's Office. Our hearts are broken tonight.

"This was an unprovoked attack. Deputy Goforth left behind a wife and two children. Please continue to pray during this difficult time."

Harris Country District Attorney Devon Anderson became emotional during a Saturday afternoon press conference as she said: "It is time for the silent majority in this country to support law enforcement.

"There are a few bad apples in any profession - that doesn't mean there should be open warfare declared on law enforcement.

"What happened last night is an assault on the very fabric of our society."

Sheriff Ron Hickman blamed a nationwide climate of anti-police rhetoric for the "cold-blooded" killing.

"We've heard black lives matter, all lives matter. Well, cops' lives matter, too."

As he spoke, #BlueLivesMatter was trending on Twitter.

Officials said Deputy Goforth had driven to the service station at Telge and West after responding to a routine traffic accident around 30 minutes earlier.