BANGKOK (THE NATION/ASIA NEWS NETWORK) - The families of Briton David Miller, 24, and fellow traveller Hannah Witheridge, 23, who were killed on Thailand's Koh Tao Island on Monday, have paid tribute to them, issuing emotional statements through the British Foreign Office speaking of their losses, as autopsies on their bodies were completed and the results released.

A Miller family statement said: "David was an artist by temperament, so talented. He had a creative eye that he carried with him through life and in his degree.

"He was hardworking, bright and conscientious, with everything to look forward to.

"David was very giving to his family and friends and we all adored him. He will be sorely, sorely missed."

A promising student, Mr Miller had been travelling across Asia after finishing a civil and structural engineering degree at Leeds University in June. He wanted to return to Britain in the autumn to complete a Master's degree.

He had worked as an intern in the St Helier offices of Australian mining company Consolidated Minerals. He was returning from a placement in Australia when he stopped off in Thailand for a holiday. Mr Miller's family said he was due to leave Thailand on Tuesday.

Flags flew at half mast at Britain's Victoria College on Tuesday in tribute to Mr Miller, who was a former student of the college.

Mr Alun Watkins, headmaster at Victoria College, said: "David's tragic death, and in such dreadful circumstances, has come as a real shock to those who knew him and worked with him at Victoria College.

"He was a confident, articulate member of the college community with a good circle of friends. It is hard to comprehend how that life can have been brought to such a cruel and abrupt end," the BBC quoted Mr Watkins as saying.

Friends left tributes to Mr Miller on Facebook, describing him as a "gorgeous young man" who would be "missed by all".

The family of Ms Witheridge, who arrived on Koh Tao on Sept 12, said: "Hannah was a beautiful, intelligent, loving young woman who poured joy into the lives of all who knew her.

"She was selfless and caring and made each and every day that little bit more wonderful. Our family are utterly devastated and shocked by what has happened to our beautiful Hannah.

"To lose her in the way that we have is beyond comprehension. We are heartbroken and no words can possibly describe how we feel. As such, we would be extremely grateful to be left in peace while we come to terms with our loss."

Thailand on Tuesday sent condolences to families of the two Britons.

Thai Foreign Minister Tanasak Patimapragorn said in his note to British Foreign Secretary Philip Hammond that he has learned with profound regret and sadness of the deaths of Ms Witheridge and Mr Miller.

"On behalf of the Royal Thai Government and the people of Thailand, I would like to extend to you and, through you, our sincere condolences and sympathy to the bereaved families for their irreparable losses."

He further said he wished to reassure that the Thai government gave priority to protecting the safety of foreign nationals residing in and visiting the country.

"On this particular case, General Prayut Chan-o-cha, Prime Minister of Thailand, has personally instructed the relevant Thai authorities to tighten security measures in the area," said General Tanasak, who is also deputy premier.

The post-mortem report on Mr Miller has revealed that his death was the result of blows to the head and drowning, Dr Pornchai Sutheerakune, commander of the Institute of Forensic Medicine, said on Wednesday.

Water was found in Mr Miller's lungs, his body showed traces of being dragged and there were wounds on the back of his hands, Dr Pornchai said. The findings indicate that he fought with his attackers, was beaten and then drowned, the doctor said.

The autopsy on the body of Ms Witheridge, whose body was found near Mr Miller's, showed she also had trauma to the head. There were also traces of recent sexual activity and semen was found in her vagina and anus. The doctors will use the semen to try and identify the culprit and compare the DNA samples collected from the bodies with those from the suspects.

The doctors could not say what kind of object had been used to beat the victims but only that it was a blunt object. Dr Pornchai said he could not tell the time of death yet, because the bodies had been frozen before they were sent for the autopsy.

With the autopsies now completed, the bodies can now be claimed. However, no request for release has been made.