MEXICO CITY – Mexico City police are investigating classified advertisements posted on the Internet by people offering their services as hired killers for as little as $6,000, police said Friday.

One post on the Web site, which hosts free ads for people selling old home appliances or renting apartments, advertises the services of an “ex-military hitman, professional and discreet.”

The man promises a “job guaranteed in 10 days or less” and adds “I have worked in Spain, only serious offers, $6,000.”

A police spokeswoman said authorities were taking the ads seriously, at a time when Mexican drug cartels and organized crime gangs are going ever more public with their tit-for-tat murders and leaving bodies and severed heads in streets.

Some 1,700 people have been killed so far this year in attacks between rival cartels and the thousands of soldiers and federal police sent out to crack down on them. Gangs often use paid assassins using high-caliber weapons for their hits.

“The problem of hitmen is real and we are facing it all over the country – people offer their services to kill someone for a price,” city police official Miguel Amelio Gomez was quoted as saying in the daily Reforma newspaper.

Mexican drug gangs aired radio spots in Guatemala earlier this year seeking elite ex-soldiers to work as smugglers, and an armed wing of the Gulf cartel hung banners in towns near the U.S. border also advertising for new recruits.

One of the Internet ads, titled “Hitman – Killer for Hire,” reads: “Problems with a certain person? Want it taken care of? Write me. I am 100 percent professional and don't charge in advance.”

One advertiser, contacted by Reuters, boasted that he had ”international experience” and enough tales to write a book.

A slow and ineffective justice system means homicides in Mexico are often left uninvestigated and killers elude jail.

The website also has an ad from somebody seeking to hire a ”reliable” hitman for “an easy job” in Mexico City.

(Editing by Anthony Boadle)