The Ministry of Defence (MoD) has come under legal pressure to investigate the alleged shooting of four "innocent" Afghan youngsters during a joint security operation in Helmand province.
The victims, all boys aged between 12 and 18, were allegedly killed after British and Afghan forces entered a house in the village of Loi Bagh.
Birmingham-based Public Interest Lawyers are bringing the claim on behalf of the elder brother of two teenagers killed in the incident.
A summary of the allegations claims that at about 8pm on October 18, British and Afghan forces entered the village demanding to know where the claimant's brother Fazel Mohammed lived.
The soldiers allegedly entered the house of a neighbour, dragged him from his bed, hooded him and his son and beat them until they showed them the house.
The summary adds: "The soldiers entered the claimant's family property and shot and killed at close range four teenage boys who were sat drinking tea unarmed in the 'guesthouse'."
The four victims were Fazel Mohammed, 18, Naik Mohammed, 16, the younger brothers of the claimant, along with schoolboys Mohammed Tayeb, 14, and Ahmed Shah, 12, who were visiting Loi Bagh to attend the local madrassa.
The troops are alleged to have ransacked the house, searching for evidence but left empty handed.
After the soldiers left, relatives and neighbours found the bodies of the four teenagers lying in a line. All had apparently been shot in the head and neck region.
Tessa Gregory, of Public Interest Lawyers, said: "Our client, the elder brother of two of the teenage victims, wants to know why this happened.
"As far as we are aware no investigation into these tragic deaths has taken place.
"We hope that in light of our urgent representations the MoD will act swiftly to ensure that an effective and independent investigation is carried out without any further delay."
An MoD spokesman said: "The MoD received details of these allegations on Tuesday in a letter from a UK firm of solicitors on behalf of an Afghan national and will give them full consideration before responding."
The "letter before action" is the first stage of seeking a judicial review and requires the MoD to reply within 14 days.
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