Darkness is falling on the world's cocaine captial, and just as the shadows lengthen, fear replaces a strong regional pride in this lush mountain valley and sends residents on their way home.

Medellin dies every night of the week, around 9 p.m.A war is taking place on the streets of this city of 2 million, infamous for its association with cocaine kingpin Pablo Escobar and his Medellin Cartel of traffickers. It is here in the misery of impoverished slums that the cartel has recruited thousands of young hit men, some as young as 15 years old.

Some 180 policemen have been killed, and more than 3,000 murders have taken place so far this year, making Medellin one of the most violent cities on Earth.

As many as 60 people have been killed in a single bloody weekend. Gunmen have sprayed indiscriminate fire on street corners in the slums where the cocaine hit squads live, and 19 people were killed recently in a single massacre in a bar frequented by sons and daughters of the upper class.

There are serious accusations that some members of the National Police force, angered and frustrated by the seeming impunity with which officers are killed, have taken to massacring known or suspected cocaine hit men.

According to police reports, death squads have executed young men in homes or bars or even ice cream parlors in Medellin's poor northeastern neighborhoods where the cocaine gangs flourish.

Mayor Omar Florez said citizens' accusations of a "dirty war" with police involvement had reached his office and had been turned over to other authorities for investigation.

Semana magazine reported at least 20 massacres of that type have taken place with more than 150 people killed. Semana quoted an unnamed Medellin politician as saying, "The massacres in the neighborhoods are a retaliation for the murders of police."

"Some of the death squads are made up of members of the Metropolitan Police who, battered by the deaths of their companions and the lack of detention of those responsible, decided to apply the law with their own hands and to revenge their fallen comrades," the politician said.

Gen. Harold Bedoya, commander of the army's 4th Brigade and the maximum military authority in the city, said the "rumors" of police involvement would be investigated if made into formal accusations.

The National Police recently replaced the Medellin metropolitan commander and transferred some agents out of the city.

In the midst of the massacres, an anonymous letter appeared warning that anyone discovered after 9 p.m. in the city's numerous night clubs, restaurants and bars would be killed. The letter increased the already high level of fear and has nearly closed down the city's once strong nightlife.

"In the full season of the school vacations, precisely when a hot summer illuminates the city, many streets appear to be those of a ghost people, dark and trapped in the worst of winters," the local El Mundo newspaper said.

In the daytime, Medellin is a bustling, beautiful city of 2 million people, a place surrounded by green mountains. Small streams run down through a variety of trees where birds with bright red breasts make their home.

Its people - known as "paisas" - pride themselves on their reputation as Colombia's best businessmen. It is the rich industrial center of the country and one of Latin American's major textile producers.

But the Medellin economy also has its dark side. Migrants from rural areas have flocked to the city since the 1950s, seeking work or trying to escape the fighting between guerrillas and the army.

They inhabit the mountainsides along the northeast flank of Medellin, in neighborhoods of intense poverty. Many city services do not reach there.

Mayor Florez said about half of the city's residents live in poverty.

Business has fallen off drastically for many restaurants, bars and stores and a local chamber of commerce-type organization warned many of its 2,200 members were on the verge of closing.

Sitting in a room full of empty tables, restaurant manager Ivan Patino said his income was off by more than 50 percent.

"Yesterday there was a father and his daughter here when a passing car backfired. They dove for the ground, thinking there were explosions going off," he said.