The US has taken action against 10 people it says are protecting the former Bosnian Serb leader and indicted war criminal, Radovan Karadzic.
The individuals' financial assets have been frozen and they have been banned from travelling to the US.
Three serving Bosnian police officers and a former Bosnian Serb President have also been sacked from their jobs for allegedly helping Mr Karadzic.
Mr Karadzic, who has been charged with genocide, is still on the run.
The US ambassador to Bosnia, Clifford Bond, said there was credible information that 10 people had been providing financial and logistical support, protection and communications for indicted war criminals, including Radovan Karadzic.
Nato has repeatedly failed to capture Mr Karadzic
He said the aim of the visa ban and the freezing of assets was to disrupt the financial networks which enable war criminals to avoid arrest.
At the same time the chief international envoy to Bosnia, Lord Ashdown, announced that three Bosnian Serb police officers would be sacked from their jobs.
He said a former Bosnian Serb President, Mirko Sarovic, would also be removed from his position as Vice-President of the SDS political party, a party originally founded by Radovan Karadzic.
Lord Ashdown said some of the individuals were guilty of bribing and intimidating the police and the courts to drop investigations against them.
Radovan Karadzic, who has been charged with genocide for his part in the Bosnian war, remains free eight years after the war ended.
The international community has been embarrassed by repeated failures to arrest him.
It now seems to be adopting new tactics, getting at their prey via his friends and associates.