The freeze, first ordered in 2011, applies to all assets held in Switzerland by the toppled leaders and by "politically exposed persons in their entourage," the foreign ministry said in a statement announcing the decision.

"The aim is to give investigations in Tunisia and Egypt more time and to take account of the political transition in the two countries," it said.

On the Tunisian side, the freeze covers some 60 million Swiss francs (49 millions euros). In the case of Egypt the frozen assets amount to some 700 million Swiss francs (572 millions euros).

Switzerland has been working closely with both countries to try to determine the origin of the funds, and has already made "significant progress", the statement said.

The freeze aims to prevent any ill-gotten funds from being hidden in other financial markets, out of the reach of judicial authorities.

The family of ousted Egyptian dictator Hosni Mubarak still owns assets on British territory nearly two years after British authorities called for them to be frozen, Egypt's largest investment bank, EFG Hermes disclosed earlier.

EFG Hermes, the fund's co-owners, has admitted that "to the best of [their] knowledge" Mubarak's son Gamal has a 17.5% stake in a fund registered in the British Virgin Islands (BVI). It is 20 months since the territory's authorities issued an order calling for the freezing of Gamal Mubarak's assets.

According to EFG-Hermes, Mubarak has received around $880,000 annually from the fund since it was incorporated in July 2002, though the fund currently does not contain any "meaningful" assets.

NJF/NJF