Swiss officials say frozen Swiss bank accounts held by associates of the Yugoslav president, Slobodan Milosevic, hold more than SFr100 million ($57 million). On Tuesday the nature of the blocked accounts was also confirmed.
According to Ottmar Wyss, head of Switzerland's state secretariat for economic affairs, around half of the blocked accounts are held by individuals and the rest by companies.
He said some 30 people close to Milosevic had their bank accounts frozen, adding that it was "very possible" that the president's wife, Mirjana Markovic, had accounts in Switzerland - as suggested by sources in the Swiss banking sector.
Wyss declined to name people who had had accounts blocked. The authorities say none of the accounts are in the name of Milosevic himself.
Berne had ordered Swiss banks to inform the authorities about accounts belonging to Milosevic or his allies, but Swiss officials had not reported any finds until this week.
On Monday, the finance minister, Kaspar Villiger, told parliament that some 100 accounts belonging to Milosevic associates had been frozen.
The minister said the cabinet would examine the situation following last month's presidential election in Yugoslavia, before deciding whether it should take any further steps.
Last December, a Swiss official said several millions of francs worth of Yugoslav and Serb government assets had been frozen in Switzerland, following the imposition of sanctions earlier in the year.
In June 1999, the Swiss government froze the assets of Milosevic and four other war crimes suspects at the request of the International Criminal Tribunal for ex-Yugoslavia.
Last July Berne expanded the list in line with the European Union to cover more than 300 people close to Milosevic and Yugoslav and Serbian-controlled companies.
The court in The Hague had sought legal assistance in its prosecution of the Yugoslav leaders for alleged atrocities against ethnic Albanians in Kosovo.
swissinfo with agencies