Britain said on Monday it had sanctioned Bosnian Serb separatist leader Milorad Dodik and a second Bosnian-Serb politician for what it described as their attempts to undermine the legitimacy and functionality of Bosnia and Herzegovina.
Bosnia has been going through its worst political crisis since the end of the Balkan wars of the 1990s, with Bosnian Serbs challenging state institutions as part of their longtime bid to secede and eventually join neighbouring Serbia.
The sanctions on Dodik and Zeljka Cvijanovic, President of the entity of Republika Srpska, include travel bans and asset freezes, the government said.
"These two politicians are deliberately undermining the hard won peace in Bosnia and Herzegovina. Encouraged by (Russian President Vladimir) Putin, their reckless behaviour threatens stability and security across the Western Balkans," British Foreign Secretary Liz Truss said in a statement.
Britain said Dodik had "driven action to withdraw Republika Srpska from key State institutions, using divisive, dangerous, nationalist rhetoric, undermining domestic and regional peace and encouraging ethnic hatred and genocide denial."
Cvijanovic has publicly glorified war criminals and denied the genocide at Srebrenica, the British government said.
The United States sanctioned Dodik, who is the Serb member of Bosnia's inter-ethnic tripartite presidency which makes decisions on the Balkan country's foreign policy, in January.
(Reporting by Kylie MacLellan; Editing by Kate Holton)