BERN, Switzerland (AP) _ With Mobutu Sese Seko apparently toppled from power in Zaire, Switzerland said Saturday it is ordering a one-year block on any assets held here by the ousted ruler and his family.

Mobutu, 66, reputedly is one of world's richest men after three decades in control of his diamond- and mineral-rich country. He long has been rumored to have stashed up to $4 billion in Switzerland.

But he also has been a big spender, and little is known about how much of the fortune he may have spent in his attempt to retain power.

Swiss banks have said they cannot find any accounts. The government has asked banking regulators to search again and the banking commission said it would survey all 400 Swiss banks.

The Federal Council ordered all managers of the family's assets in Switzerland to report immediately to the Federal Finance Department.

Switzerland said Friday it would block any sale of the first asset it had identified, a $2.75 million estate above Lake Geneva. The action, it said, came in response to a request from the prosecutor in Lubumbashi, Zaire _ the headquarters of the rebel forces.

Rebels entered the Zairian capital of Kinshasa on Saturday, a day after Mobutu left the city and handed control of the country to his Cabinet.

Foreign Ministry official Matthias Krafft said the order in no way implies recognition of a new government for Zaire, and that it was too soon for the Swiss government to have had contact with the new rulers.