A new report by Human Rights Watch says gangs still operate freely in the crime-plagued port city of Buenaventura, with criminals carrying out murders and dismembering victims at an alarming rate a year after Colombia created a special task force to curb violence there.

President Juan Manuel Santos a year ago sent additional police and prosecutors to boost security in what has long been one of Colombia's most-violent cities and a haven for paramilitary groups and drug traffickers.

Murders have declined and arrests have gone up since then. But the report released Wednesday says gangs comprised of former right-wing paramilitaries still control entire neighborhoods, extorting businesses and threatening women with rape.