A dozen of US secret service agents assigned for President Barack Obama at an international summit in Colombia have been relieved of duty after allegations of drinking and consorting with prostitutes.

There have been allegations of misconduct made against Secret Service personnel in Cartagena, Colombia, prior to the president's trip, agency spokesman Edwin Donovan said in a statement.

Because of this, those personnel are being relieved of their assignments, returned to their place of duty, and are being replaced by other Secret Service personnel.

According to Donovan, the allegations of misconduct were related to activity Friday afternoon before the President arrived in Cartagena, Colombia, to attend the summit.

However, Donovan did not specify what allegations had been made against the secret service agents but said the issue had been turned over to the agency's Office of Professional Responsibility.

These personnel changes will not affect the comprehensive security plan that has been prepared in advance of the president's trip, Donovan said. The Secret Service takes all allegations of misconduct seriously.

The allegation is related to at least one agent having involved with prostitutes, the Washington Post reported quoting Jon Adler, president of the Federal Law Enforcement Officers Association.

Obama attended a dinner party at Cartagena's historic Spanish fortress Friday night. He was due to attend meetings with more than 30 leaders Saturday and Sunday.

The allegation news broke when four home-made explosives devices -two in Cartagena and two in the Colombian capital Bogota- went off later Friday near the US embassy, police said.

However, Donovan maintained that the Secret Service staffing changes will not affect the comprehensive security plan that has been prepared in advance of the president's trip.

The Secret Service takes all allegations of misconduct seriously. This entire matter has been turned over to our Office of Professional Responsibility, which serves as the agency's internal affairs component, he added.