JOHOR BAHRU - More than a dozen robbers stormed into a supermarket and two cellphone shops in a Johor suburb and escaped with RM30,000 (S$12,575) in cash and mobile phones within a minute.

Brandishing parangs, they arrived on motorcycles and broke up into three groups in Taman Air Baru, Pasir Gudang, on Thursday evening, police and witnesses said.

The incident occurred at about 7pm, and was believed to be the first time that a group of criminals had walked into several shops at once to rob.

The biggest Chinese-language newspaper, Sinchew Daily News, said 30 armed robbers were involved.

At the Jiason Supermarket, the men rushed to the cashiers and demanded money.

'They held our cashiers at knife-point. It happened so fast and they escaped within one minute,' said supermarket manager Tiong Foon Kai, 34.

He said the robbers took about RM13,000 of the day's collection.

Nelson Ng, 17, who was behind the counter at one of the

mobile-phone shops about 50m away, said seven men came in and broke the glass showcase by stepping on it.

'One of them held me while the others grabbed 20 cellphones,' he said, adding that he was lucky not to be harmed.

He estimated the shop's losses at RM11,000.

At the third shop, a worker, who wanted to be known only as Chong, said the robbers took 31 cellphones and RM2,000 in cash.

'It was over in a minute. The robbers planned it well,' he said.

Superintendent Roslan Zainuddin, the police officer in charge of the Seri Alam district where the incident occurred, said police were tracking down one of the suspects who had a record of drug-related offences.

'We have not ruled out the possibility that they were under the influence of drugs and responsible for other robberies,' he added.