A prominent U.S.-based human rights group on Thursday accused Bulgarian police of using violence, intimidation and arbitrary arrest against street children, who are mostly of Roma origin. In a report based on interviews with children in five Bulgarian cities including Sofia, Human Rights Watch also condemned the practice of sending troublesomeminors to workhouse-style institutions where conditions are usually very hard.``The street children are often exposed to harrassment and physical violence from the police both on the street and while in detention,`` the report said. Children may be kept in detention for days on endand are sometimes subjected to sexual harrassment, it added. The children are also vulnerable to racially motivated attacks from gangs of skinheads.The police, who regard the children as a major source of petty crime, generally disregard the attacks, the report said. Police officials said they would respond to the report's findings in the near future. An estimated 14,000 children scrape a living on Bulgaria's streets by begging, pickpocketing and sifting through rubbish heaps. Bulgarianmedia, which show little sympathy for the street children, say mostlive with their parents and are sent out each morning to locationslike railway stations deemed lucrative for their activities. Human Rights Watch urged the authorities to punish policemen who abuse the children, to make a special investigation of racial attacks, to scrap ``workhouses`` and to set up a separate judicial system forunder-aged offenders.The non-governmental group, which is privately funded and was established in the United States 20 years ago, monitors and promotes the observance of human rights accords worldwide.