British boy Ashya King has undergone his first proton beam therapy session for a life-threatening brain tumour in Prague, a week after the five-year-old boy was flown in from Spain.

Ashya's case caused an international uproar after his parents removed him from an English hospital last month without doctors' consent, sparking a police manhunt.

Ashya's parents, Brett and Naghmeh King, had fought a protracted battle for proton beam treatment, which targets tumours more directly than radiotherapy, but is not yet available for patients in Britain.

The treatment for Ashya was the first of 30 planned radiation sessions, Prague Proton Therapy Centre said, combined with chemotherapy to be applied at the city's Motol hospital, where the boy was admitted last week.

Spanish police arrested Ashya's parents on August 30. They had travelled to Spain to sell a flat they owned there to raise funds for the Czech treatment privately.

They spent a night in jail, but were released after British authorities cancelled an arrest warrant.

The case has ignited debate in Britain over children's health rights.

Now, an 11-year-old Czech boy who had the same disease as Ashya and was treated with proton beam therapy has spoken out.

Miki Roth told reporters: ''He (Ashya) can't say to himself: 'I'm ill, so I'm not going to do anything.'

''He should read or exercise, try to walk, exercise his legs with therapists that visit him.''

Miki was diagnosed with medulloblastoma about two years ago. Following surgery, he received treatment at Prague's Proton Therapy Centre.

The treatment worked well for Miki, who was in a wheelchair when he arrived at the centre. He was able to walk on his own after 30 sessions, followed by a year of chemotherapy at Motol hospital.