Serbian police detained one person for questioning on Tuesday in the latest effort to gather clues leading to war crimes suspect Ratko Mladic, whose arrest is key to the country's EU bid, a war crimes prosecutor said.

Although the Bosnian war ended 15 years ago, the fate of the burly Bosnian Serb wartime commander casts a long shadow over Serbia's fate today as the European Union insists on his arrest before Belgrade can make progress toward joining the bloc.

Early on Tuesday morning the police began a search of several premises in Belgrade and in the central town of Arandjelovac, 75 km (46 miles) south of the capital.

"We were looking for material evidence and individuals to lead us to Mladic. One person was detained for questioning," deputy war crimes prosecutor Bruno Vekaric said, without giving further details.

Serbian officials are anxious to show they are focused on the issue after EU foreign ministers last week decided to ask the bloc's executive commission for an opinion on launching entry talks with Serbia. Earlier, they had blocked this procedural step in the long accession process over Mladic.

The International Criminal Tribunal for the former Yugoslavia (ICTY), a United Nations war crimes court,  has indicted Mladic for genocide in the 1995 massacre of over 7,000 Muslims in the Bosnian town of Srebrenica and the 1992-95 siege of Sarajevo.

Last week the government raised a reward for any information leading to Mladic's arrest to 10 million euros.

In May, Mladic's family launched court proceedings to declare him dead on the grounds he had been in poor health and they had had no contact with him for more than five years.

A security official said Mladic is believed to be alive and probably within Belgrade city limits.

"We are sure he is alive. We are trying to establish the way his finances work, to see how he can get medical help," said an operative who asked not to be named. "However elusive, he will have to surface somewhere and we will be there waiting."