An off-duty Indonesian police officer who was assaulted in Central Java by men from a martial arts group has been flown to Singapore for treatment.

On May 8, Mr Aditya Mulya Ramdhani, 35, was set upon by men armed with bamboo sticks - a vicious attack which left him with severe head trauma. He was not in uniform then.

The former head of the Criminal Investigation Unit in the Wonogiri regency, located in Central Java, has been in a coma since the attack.

A family friend suggested that Mr Aditya's wife, Madam Dewi Setiyowati, contact a doctor in Singapore to have Mr Aditya moved to the Republic for further treatment.

Madam Dewi , 40, said this doctor visited her husband at the Dr Oen Solo Baru Hospital and made arrangements for the couple to be flown to Singapore.

On May 16, Mr Aditya was warded at the Singapore General Hospital (SGH).

Madam Dewi, a housewife, said in Bahasa Indonesia: "I never expected this to happen. I know that police work is dangerous, but in our 11 years of marriage, he always came home safe."

Based on Indonesian media reports, the officer had attempted to disperse the men who were seen destroying public property.

Reports said Mr Aditya was attacked after he was mistaken for a member of the rival martial arts group.

Madam Dewi said the doctor helped pay some of the costs involved in transferring her husband to Singapore. But there is still the hospital bill, which was in excess of $50,000, as of May 27.

Although she has made some payments, she showed The Straits Times a copy of the invoice which indicated she currently owes over $22,000.

Madam Dewi said the Indonesian police have agreed to cover all medical costs incurred by Mr Aditya from May 29 onwards, a day after he was transferred from the Intensive Care Unit to a general ward at SGH.

She is hoping the Indonesian police will cover earlier medical costs as well, along with the cost of their flight. The officer's friends, colleagues and family members have chipped in to reduce the costs.

"Right now, my main priority is for (my husband) to regain consciousness, and for us to reunite as a family as quickly as possible," said Madam Dewi, a mother of three children, aged 10, nine and four.

She said the children are being looked after by family members in Indonesia and are unaware of their father's condition.

She hopes that her husband will recover in time for Hari Raya Puasa, which falls on June 4 in Indonesia, so that they can celebrate as a family in Central Java.

The attack has riled up Indonesians, with many taking to social media to condemn the attackers.

At a press conference in Central Java on May 29, the Indonesian police said nine suspects have been apprehended for their role in the attack.

One suspect was later released as he is a minor.

For assault, the suspects could potentially face up to nine years in prison.