Fourteen current and former law-enforcement officers are among 20 defendants charged in Mississippi and Tennessee with accepting bribes from drug traffickers for police protection in what officials called "a monumental betrayal of public trust".

The arrests follow a years-long investigation by federal agents who posed as narcotics dealers. Two of the defendants were Mississippi sheriffs.

Federal officials set up the sting after hearing complaints from real drug traffickers about having to pay bribes to officers.

The bribery network allegedly extended beyond the Mississippi Delta region into Memphis, Tennessee, and Miami, Florida.

"The original complaints that began the investigation were from drug dealers," US Attorney Clay Joyner for the Northern District of Mississippi told a news conference on Thursday.

Some of the officers had received bribes of between $20,000 (£15,000) and $37,000, the prosecutor added.

The sting involved undercover federal agents posing as drug dealers with fake narcotics, which the defendants allegedly believed to be 25kg (55lb) of cocaine.

FBI deputy director Andrew Bailey said the accused officers had "sold out the public".

"They betrayed the trust that the public placed in them, disgraced the badge and undermined the hard work of good law enforcement officers across this state and region," Bailey told the news conference.

The arrests come as US officials have embarked on air strikes in South America against alleged drug traffickers.