Germany's market regulator announced a ban Tuesday on so-called naked short-selling of euro zone government debt certificates and shares of major financial companies, a move aimed at upholding financial stability amid the debt crisis.

The regulator, BaFin, said the ban — which was to take effect at midnight Tuesday and run through March 31 next year — also would apply to some credit default swaps.

Naked short-selling involves a trader selling shares or investments he doesn't own. Credit default swaps are a type of insurance against a borrower going bankrupt that have become a lucrative market for traders.

European leaders have complained that speculators used credit default swaps on Greek government debt to bet the country would default on its borrowings — raising pressure on the country to the point where it was forced to ask for a bailout.

BaFin cited the "extraordinary volatility" afflicting euro zone countries' debt certificates and the widening of spreads on credit default swaps for several nations.

"Against this background, massive short-selling of the affected debt certificates and the conclusion of naked CDS on loan default risks of euro zone states would have as a consequence further excessive price movements," BaFin said in a statement.

Those could lead to "significant detriment for the financial market and could endanger the stability of the whole financial system," it added.

The ban on naked short-selling of financial companies' shares applies to several banks — Aareal Bank AG, Commerzbank AG, Deutsche Bank AG and Deutsche Postbank AG.

It also covers insurer Allianz SE; reinsurers Hannover Re AG and Munich Re AG; Generali Deutschland Holding AG, MLP AG, and Frankfurt stock exchange operator Deutsche Boerse AG.