Closing arguments have begun in the genocide trial of former Bosnian Serb leader Radovan Karadzic, with U.N. prosecutors arguing he should be sent to prison for life if found guilty.

Karadzic, who was the top political leader of the breakaway Bosnian Serb Republic during the 1992-1995 Bosnia War, says he is innocent.

In opening remarks Monday, Prosecutor Alan Tieger said Karadzic bragged about his policy of "ethnic cleansing" of non-Serbs from parts of Bosnia at the time but now denies it, promoting a "revisionist history."

Karadzic is charged with 11 crimes in all, including genocide during the 1995 massacre of thousands of Muslim men and boys in Srebrenica.

He went into hiding after the war but was caught in neighboring Serbia in 2008 and went on trial in 2009.