LONDON -- A minister in Britain's Foreign Office accused the government of Syrian President Bashar Assad on Thursday of effectively murdering a U.K. doctor held in Syrian custody, saying there is no excuse for the treatment of Dr. Abbas Khan.

Khan, a 32-year-old orthopedic surgeon from London, was seized by government troops in Aleppo, Syria, in November 2012 after he entered the country on a humanitarian mission. He appeared to be on the verge of being released when news of his death was announced.

Hugh Robertson, charged with the Foreign Office's Mideast remit, said in a televised statement that "there is no excuse whatsoever for the treatment that he has suffered by the Syrian authorities." In an unusually direct attack on Syrian officials, Robertson accused them of having "in effect murdered a British national who was in their country to help people."

Syria's Deputy Foreign Minister Faisal Mekdad told the BBC that Khan took his own life.

"He took off his pajamas, hooked it to something in the window ... and committed suicide," Mekdad said in comments broadcast late Tuesday. The claim was dismissed as "utter nonsense" by Khan's brother, Shah Nawaz.

Khan's death appears to have come only days before he was due to be freed, according to British lawmaker George Galloway, who had been negotiating with Syrian authorities to secure the doctor's release. Galloway said he'd been told that Assad himself had ordered the doctor's release and that Khan had been expected home before Christmas.

"I was in the process of booking a flight for this Friday when I got the appalling news," he said.

Prisoners of Assad's regime are routinely subjected to terrifying abuse, and Khan said in letters cited by the BBC that his captors had repeatedly beaten him for sport - and that he'd even been forced to abuse other prisoners.

The claims aren't unusual. More than 1,000 people are thought to have died in the custody of Syrian state security, according to London-based Amnesty International.

The Foreign Office said Syrian authorities have consistently ignored requests for consular access to Khan and information about his detention.

Galloway called for clarification about the circumstances of Khan's death.

"This is heartbreaking and devastating news for his family, who have been working so hard for so long to secure his release," he said.

AP reporters Raphael Satter in London and Albert Aji in Damascus, Syria, contributed to this story.