The Indonesian maid arrested over the deaths of her employers in Singapore had planned the murder, according to national police spokesman Setyo Wasisto.

"Based on the facts of the case, it may be considered a premeditated murder. She had planned the act, down to buying rope and tape (to restrain her victims)," he said in Jakarta yesterday.

Indonesian maid Khasanah, who was on the run for almost a week after her employers, Mr Chia Ngim Fong, 79, and his wife, Madam Chin Sek Fah, 78, were found tied up and later pronounced dead in their Bedok flat, was arrested last Tuesday night. She had been working as a maid in Singapore for only about a month.

The 41-year-old was arrested in Indonesia's Tungkal Ilir, in Jambi province, after local police raided her room at Hotel Nanber following a tip-off from residents.

At the time of her arrest, Khasanah was in the midst of planing to leave for Java, said Hotel Nanber owner Syartini who, like many Indonesians, goes by only one name.

Khasanah had fled Singapore by the time her elderly employers were found dead in their flat.

Inspector-General Setyo could not confirm how Khasanah left Singapore or entered Indonesia. But a source in Singapore familiar with the investigation had told The Straits Times on Sunday that she had left Singapore using her passport but was not stopped as her crime had not yet been discovered.

On the possible jail sentence that Khasanah may face if convicted, Inspector-General Setyo said: "Could be 20 years, or could even be a death sentence at maximum."

Khasanah is now in the national police detective unit's lock-up. She will not be handed over to Singapore but, instead, Indonesian investigators and their counterparts from the Singapore Police Force will work together to solve the crime.

This is because Indonesia adopts the principle of "personaliteit", police had said earlier. Personaliteit requires that any Indonesian arrested in the country for a crime committed overseas be processed in Indonesia instead of being sent to the jurisdiction where the offence took place.

National police chief Tito Karnavian also confirmed to reporters yesterday that Khasanah's prosecution will have to be in Indonesia, as per the Indonesian criminal code's stipulation that the police force must comply with.

He added that the trial will be held at the Central Jakarta District Court.

"We will bring all the witnesses to the court here. This is like the murderer Oky's case, where the crime took place in the US and the witnesses were from there," General Tito added, referring to the case of Indonesian businessman Harnoko "Oky" Dewantono, who was sentenced to death in 1995 for murdering his brother Eri Triharto Darmawan, girlfriend Gina Sutan Aswar and an American business partner in the United States, Mr Suresh Michandini, in November 1992.

Oky, described as an uncivilised killer by the judges, committed the crime while under the influence of cocaine after arguing over a business deal with his victims.

• Additional reporting by Francis Chan