Just over 49 percent of the murders committed so far this year in Puerto Rico were drug-related, according to police statistics released on Thursday.

That figure represents 490 people who were murdered for reasons linked to the drug trade, which uses the Caribbean island as a "bridge" to smuggle drugs to the U.S. mainland.

Part of those illegal drugs coming from South America remains in Puerto Rico for local consumption and becomes a lucrative business for rival gangs.

The large quantity of weapons circulating illegally on the island facilitates the "war" between gangs over control of drug corners, located mainly in Puerto Rico's public housing projects.

The island will reach 1,000 murders so far this year by next weekend, in all likelihood.

At the current murder rate of 3.1 killings per day, the U.S. commonwealth will finish 2011 with 1,135 violent deaths and a murder rate of 30.5 per 100,000 residents.

The figures show that 87 percent of the violent deaths in Puerto Rico were committed with firearms.

The wave of violence is not restricted to drugs, with 14.5 percent of the murders - or 144 deaths so far this year - being revenge killings.

Fights and arguments led to 12.2 percent of the murders, while 6.7 percent were committed during robberies and the rising number of incidents of domestic violence amounted to 2.7 percent of the killings.

Some analysts have said that one of the reasons that murders are on the rise in Puerto Rico, now exceeding the yearly record of 995 killings set in 1994, is that only 42 percent of the killers have been caught.

That impunity, according to the analysis, has contributed to the continuation of the murder wave, which is resulting in growing insecurity among the Puerto Rican public.

The worrying situation on the island led the leader of the main opposition Popular Democratic Party, Alejandro Garcia Padilla, to ask the National Guard to watch the coastlines, ports and airports to try and prevent the entry of drugs and weapons.

The National Guard was deployed on the streets of the island 18 months ago on joint patrols with the police, a measure that has not reduced the crime rate but has led to complaints over its high cost.

Garcia Padilla, in an effort to improve the situation, proposed buying better equipment for the police and reestablishing within the department a separate investigative command.