Sources in the law enforcement agencies said it is very difficult for them to deal with these cases as members of these groups cannot be kept in the custody in most of the cases because of their influential parents or patrons, leaving scopes for further crimes.

It has been learnt that most of these criminals are drug addicts. They are addicted to brown sugar or Yaba, a popular drug among the youths from posh and rich families. They are getting involved with crimes like mugging, carjacking and others.

After arresting a number of youths involved with such crimes in the last few months, the law enforcers felt how difficult it was to deal with them. The law enforcement agencies believe a number of such criminal groups are now active in the city.

Several months back police arrested sons of Chief Whip Khandaker Delwar Hossain on charge of extortion. They were later accused of carjacking.

Earlier this month three such alleged muggers were caught red-handed by the public at Rampura where one of them was killed in mob beating.

Abul Kalam Azad, one of three alleged muggers is son of a millionaire. Dipu, another accused, is a rich businessman and husband of a newscaster of a private television channel. Biltu, who died in mass beating, is son of a government high official.

The Detective Branch (DB) of police has identified a number of such groups and branded them as "VIP group" of criminals.

"These people are mostly drug addicts. One would be amazed to know that people who drive luxury cars like Prado or V-6 are committing a petty crime like mugging," said a high official of DB, Dhaka Metropolitan Police (DMP).

DB has assigned several teams with special duty to identify and arrest these groups.

Psychiatrists say the main reason of rich people's involvement in crimes is drug addiction.

"Apart from addiction, some of them may commit such crimes due to disorder of their personality. Another reason is -- most of the young people are adventure lovers and they find adventure in such criminal activities," said Dr Dewan Abdur Rahim, a psychiatrist.

Police officials believe that most of these 'VIP' criminals feel that they can get away thanks to having a rich parent or close connection with influential people in society.

"We arrest 10 to 15 such criminals every month but have to set free 90 percent of them without taking any action as we get calls from influential people to do so immediately after arresting them," he added.