A shot fired from an army watchtower near the Irish border killed a young civilian Sunday, according to a military statement that expressed regret at his death. Witnesses said 23-year-old Aidan McAnespie was shot in the back while walking to a regular weekly Gaelic football game in Aughnacloy, County Tyrone, near the border with the Irish Republic. The Dublin government immediately requested details of the shooting, which comes at a time when relations between Britain and the Irish Republic have been severely strained. The Royal Ulster Constablulary said a soldier at the vehicle checkpoint was in military custody and the shooting was under investigation. An army statement said it ``deeply regrets'' the death, which it said occurred when a weapon was fired from an observation tower at the permanent military checkpoint near the village. McAnespie, who lived in Aughnacloy, was said to have worked at Monaghan in the Irish Republic, according to Press Association, the British domestic news agency. Relations between Britain and Ireland have been severely strained recently after two British decisions concerning sectarian warfare in the predominantly Protestant British province of Northern Ireland. Britain's Court of Appeal upheld the convictions of six Irishmen sentenced to life in prison for two Irish Republican Army bombings that killed 21 people in 1974. The court rejected arguments that new evidence undermined the confessions and forensic findings that sent them to prison. The IRA is fighting to end British rule in Northern Ireland and unite the province with the Irish Republic, which is predominantly Roman Catholic. Britain also decided last month not to prosecute any Northern Ireland police officers connected with the police shootings of unarmed Roman Catholics in an alleged ``shoot-to-kill'' policy against Irish nationalist guerrillas.