BELGRADE INSISTS that last week's arrest of Bosnian Serb wartime leader Radovan Karadzic will shortly be followed by that of his military commander, Ratko Mladic. But despite the clamour of speculation that has followed Karadzic's arrest, many observers are less than convinced about how easy this will be, warning that the international community must maintain pressure on Serbia if Mladic, too, is to be brought to justice.

Serbian accession to the European Union - the platform on which the newly elected government campaigned - is tied to it arresting all those indicted by The Hague tribunal. But Mladic's enduring popularity among nationalists and the military makes this task more difficult, analysts say.

Dusan Ignjatovic, director of the Office of the National Council for Co-operation with the Tribunal, said Serbia had shown it had the political will to capture both Mladic and another fugitive, Goran Hadzic, president of a self-proclaimed Serb state inside Croatia during the war.

"We have shown that nobody was protected and that it is a matter of days before Mladic and Hadzic will be at the tribunal," he insisted.

Karadzic, the wartime president of Republika Srpska, was arrested on Monday on charges of genocide, murder, extermination and deportation of Bosniaks, Croats and other non-Serbs between 1992 and 1995. He is also accused of orchestrating the 1995 Srebrenica massacre, which international courts have defined as genocide.

According to a source close to the investigation, the government has released few details about the Karadzic operation to avoid jeopardising plans to arrest Mladic. Karadzic's detention is the prelude to Mladic's, the source added.

Last month's capture of Stojan Zupljanin, the former Bosnian Serb security chief, is said to have revealed new information about Mladic's support network.

"I think there's an ongoing search and investigation and I don't think the authorities want to reveal whichever means they were using to get on the tail of Karadzic," said Ivan Vejvoda, director of the Balkan Trust for Democracy in Belgrade.

The departure of the head of the security intelligence service, the BIA, Rade Bulatovic, following the formation of a new pro-European government is also being seen as a decisive factor.

"It is quite clear that the arrest of the remaining tribunal fugitives was possible when prime minister Vojislav Kostunica stepped down from power and Rade Bulatovic left the BIA," said Dejan Anastasijevic, a Belgrade journalist and political analyst. "Radovan Karadzic would never have been captured if Rade Bulatovic had stayed the chief of BIA."

Natasa Kandic, who heads the Humanitarian Law Centre in Belgrade, said that with Kostunica out of power, Mladic could yet find himself in court.

"After Karadzic's arrest, freedom no longer exists for Mladic," she said.

The long wait for Karadzic's arrest was not due to ignorance of his whereabouts, but rather to a lack of will to take action, say analysts.

"The BIA always knew where he was, that's pretty much an inescapable conclusion," said James Lyon of the International Crisis Group. "In Serbia, they've known where these people are all along."

It might prove harder to arrest Mladic, who is thought to be in hiding and surrounded by loyal followers, unlike Karadzic who was openly practising alternative medicine under an assumed name at a clinic in Belgrade.

Mladic also has many nationalist supporters in Serbia who believe he was fighting for all Serbs, to protect them from Muslims and Bosnian Croats.

"Karadzic was never that popular here in Serbia, and Mladic was," said Lyon. "Mladic is viewed as a genuine war hero."

There are also concerns that the Serbian army, which is known to have helped detain Karadzic, might be unwilling to play such a prominent role in Mladic's arrest given past allegiances.

"Mladic is rumoured to have much better security around him and a much better web of protection including a huge number of former military people who were loyal to him on a personal basis," said Lyon. "So I think the difference between arresting Karadzic and arresting Mladic should not be underestimated."

Since May of last year, however, the army has been under the control of President Boris Tadic and his Democratic Party, which has helped reform it, Serbian commentators say.

"The people who are heading the army's secret service and the regular secret service are a little bit removed from the 1990s war and the war policy and all the things that can be linked with Ratko Mladic," said Milan Antonijevic, of the Lawyers' Committee for Human Rights in Belgrade.

Vejvoda, of the Balkan Trust For Democracy, agreed that the tone of the new government meant the odds were stacked against Mladic remaining a free man.

"I think that military intelligence has co-operated and that they will do the same thing now with Mladic," he said.

Officials in Brussels have been very enthusiastic about the future since Karadzic's arrest.

"Karadzic's arrest proves the determination of the new government to achieve full co-operation with the tribunal," EU enlargement chief Ollie Rehn told reporters.

The head of EU foreign policy, Javier Solana, was no less positive, saying: "We have to talk to the prosecutor of the international tribunal, but I am almost certain he is going to say there is full co-operation between Serbia and the tribunal."

But some observers are warning against accepting Serbia's change of heart at face value, especially when only last month the tribunal's president, Fausto Pocar, was criticising the state for failing to make arrests.

The foreign ministry of the Netherlands, the last EU state to agree to offer Serbia a pre-accession deal in April, is still lukewarm, describing Karadzic's arrest as only "a step in the right direction".

"For the Netherlands, it is very important that Mladic will also be arrested," said Rob Dekker, a foreign ministry spokesman.

Some worry that too much praise could actually undermine efforts to arrest Mladic, and encourage the Serbian government to rest on its laurels.

"Judging by the way Rehn and Solana are acting, it appears the pressure (to arrest Mladic) might ease," said Lyon.

The carrot of EU membership has been a powerful tool in securing the arrest of war crimes suspects in recent years, particularly in Croatia, but now also in Serbia.

"In the past we've seen Serbia come up with a suspect out of its hat to keep the EU happy," Geraldine Mattioli, advocacy director at Human Rights Watch, pointed out.

Mattioli argues that the EU's Stabilisation and Association Agreement (SAA) should not be ratified until the remaining arrests have been made.

"The EU member states that are about to ratify the SAA with Serbia would do better waiting to make sure this willingness is indeed there and that speculation is met by action; that Mladic is arrested and surrendered," she said.

Antonijevic agrees that the international community has a crucial role to play and that it should continue to apply pressure.

"Mentioning Ratko Mladic in EU statements is something that is really needed for further arrests," he said.

This article is published courtesy of the Institute for War and Peace Reporting