The "excellent news" of the arrest of war crimes suspect Ratko Mladic will serve as a warning to others, UK Prime Minister David Cameron has said.
"International law has a very long reach and a very long memory," he said.
Foreign Secretary William Hague said the regime in Libya should take note.
Gen Mladic, commander of the Bosnian Serb army during the 1992-95 war, was Europe's most-wanted war crimes suspect for alleged crimes including a key role in the 1995 Srebrenica massacre.
He was indicted by the UN war crimes tribunal in The Hague in 1995 for crimes including genocide over the Srebrenica massacre - in which at least 7,500 men and boys were killed - the worst single atrocity in Europe since World War II.
He disappeared after the arrest of former Yugoslav President Slobodan Milosevic in 2001 and became the most prominent Bosnian war crimes suspect still at large, after former Bosnian Serb leader Radovan Karadzic was arrested in 2008.
Mr Cameron said: "This is excellent news because we have to remember this man stands accused of some absolutely horrific war crimes.
"And I think today of all days we should remember the thousands who died in Srebrenica and in the siege of Sarajevo - some of the most terrible things that have happened in recent decades on our continent."
The prime minister added: "People should recognise that it's right that international law has a very long reach and a very long memory. It will send a signal to war criminals everywhere: 'In the end we'll get you.'"
Mr Hague said Col Gaddafi's regime in Libya - which has carried out a brutal crackdown on anti-Gaddafi protesters - should take note.
"These things do not get forgotten," he told the BBC. "For any members of that regime who are contemplating anything that makes them complicit in war crimes, or crimes against humanity, this does carry an important lesson for them."
For Labour, shadow foreign secretary Douglas Alexander said the arrest showed that "however much you hide and however much you run" no-one could hide from justice.
"There have been many people over many, many years who have been working for this outcome and I think we owe it to the victims of the terrible massacres in Srebrenica and Sarajevo that he now faces the full force of international law."
And he added: "It does, I think, remove one of the significant obstacles, perhaps the most significant obstacle, preventing Serbia being able to move towards a securer European future."
Former prime minister Tony Blair said: "This is a huge moment for the principle that people who engage in genocide will eventually be brought to justice, but also for Serbia.
"They have taken that action, which is enormously difficult for them inside their own politics and country."
He told Channel 4 News that it was "an interesting example ... of the way that Europe and the prospect of European Union membership can act as a magnet for changing the behaviour of countries changing their political system".
Former Liberal Democrat leader Lord Ashdown, who was High Representative for Bosnia and Herzegovina between 2002 and 2007, also welcomed the news and said his trial would be "a chance for the whole Balkan region to put the past behind them".
Conservative MP Col Bob Stewart, who commanded UN troops in Bosnia in 1992, told the BBC: "It is very, very important that this man Mladic is brought to The Hague quickly, the trial starts quickly, the trial is expeditious in dealing with the matter and, actually, at the end of it justice prevails."