The family of a teenager murdered in an execution-style hit have appealed for an end to the reign of violence on Keighley's streets.

In the six months since Yasser Hussain Nazir was gunned down on the forecourt of a petrol station, three other young Asians from Keighley have been killed in what are thought to be gang-related attacks.

Murder squad detectives said they are hunting the "final piece of the jigsaw" to catch Yasser's killer - a move which the 16-year-old's family believes could restore peace to the town.

This week Yasser's brother, Mohammed Sadique, 24, said: "Losing him has ripped the soul out of our family. We have not been the same since. We all used to spend happy days together but they have gone since he died and I don't think they will ever come back."

Speaking from the family's home in Chatsworth Street, Keighley, Mr Sadique said: "The police say they are very close to the people who did this and that they just need a bit more information. We would appeal to anyone who knows anything to speak to them - and to help stop the violence in this town.

"If Yasser was here, he would want this all to stop. Our family wanst these killings to stop."

Mr Sadique, a production operative, said it was unclear if it was Yasser or the two friends in his car who were the target of the well orchestrated ambush.

"Yasser would not have done anything to provoke this. We all do silly things when we are young but he wasn't a bad lad," he said.

"He was a great son and brother to have around. He could have done anything with his life, he could have been anything. We will never know now."

Detectives have interviewed more than 300 people about the murder at the Shell filling station in Haworth Road, Bradford, on September 5, last year.

Although 15 people have been arrested and questioned, it remains the only case in the string of killings involving young people from Keighley where no-one has been charged.

Yasser had just pulled into the filling station when a gunman leapt out of a green Honda Accord and fired two shots into his car, both of them hitting him in the head.

Det Supt Phil Sedgwick, who is leading the investigation, said: "We have suspicions as to who the killers are. We believe that up to a dozen may have been involved in the conspiracy to a lesser or greater extent. We are not far from prosecuting the offenders, but we need that final piece of the jigsaw."

He said the public response had not been as good as they hoped.

He added: "I am sure that the identities of the killers are well known among certain sections of the community, but that has not permeated to us despite our best efforts."

While officers have probed a number of possible motives, including retribution or drugs, they have yet to deduce exactly why Yasser died. "We have examined the background of Yasser and his associates. We have looked at whether they had upset anyone," said Det Supt Sedgwick. "There are associates of Yasser's who might know the true motive behind this."

He said that while Yasser's killing may not be directly tied to the others, it would be foolish not to examine similarities between them.

"We are very interested in the personalities involved in a number of incidents in the Keighley area and how they relate to Yasser's murder," he added.

Det Supt Sedgwick said people needed to work with the police to end the cycle of violence. "If people don't come forward, criminals can operate with impunity. People need to give us the information we need to break this power base," he said.

Anyone with information should contact detectives on 01274 376225.