The parents of Britain's youngest suspected suicide bomber, described on Monday as a "typical teenager", have accused Islamic State leaders of being "too cowardly to do their own dirty work".

Talha Asmal is believed to have travelled to Syria in April with friend Hassan Munshi, also 17, and IS announced on Saturday that he was the driver of one of four explosive-ladened vehicles used in an attack on an oil refinery in northern Iraq.

Parents Ibrahim, 42, and Noorjaha, 38, said the group had preyed upon his "innocence and vulnerability".

"It appears that Talha fell under the spell of individuals who continued to prey on his innocence and vulnerability to the point where if the press reports are accurate he was ordered to his death by so-called ISIS handlers and leaders too cowardly to do their own dirty work," they said in a statement.

"We are all naturally utterly devastated and heartbroken by the unspeakable tragedy that appears to have befallen us."

Asmal was taking his final school exams, but is believed to have boarded a flight from Manchester to Dalaman in southwest Turkey on March 31.

Both youths hailed from the northern English town of Dewsbury, as did Mohammad Sidique Khan, the ringleader of four homegrown suicide bombers who carried out the July 7, 2005 bombings which killed 52 people on three Underground trains and a bus in London.

Local councillor Masood Ahmed, who knew Asmal, said there were no signs to suggest the teenager had become radicalised.

"He was a very quiet caring and loving child, he'd never been in trouble with police, at school you never heard of him being in trouble," Ahmed told BBC Radio 4. "He was just a typical teenager."

Hundreds of Britons are believed to have joined the Islamic State group in Syria and Iraq.