BRASILIA, April 24 (Reuters) - Brazil has blocked

prediction market platforms and tightened derivatives rules to

curb "bet-like" products, Finance Minister Dario Durigan said on

Friday, arguing such markets breach betting regulations approved

by Congress.

Speaking at a press conference, Durigan said 28 prediction

market platforms had been shut down in Latin America's largest

economy by telecoms regulator Anatel. Hours later, the Finance

Ministry revised the figure to 27 firms.

Websites of companies such as Polymarket and Kalshi were

offline by early Friday afternoon.

Durigan added the National Monetary Council on Thursday

defined which underlying assets may be used in derivatives

trading, banning those linked to sports events, online gaming,

or political, electoral, cultural and social outcomes.

Under the text, the council allows only derivative contracts

tied to pre-defined economic and financial benchmarks, such as

price indices, interest rates and exchange rates, effectively

barring other instruments.

Trading in such derivatives will be permitted provided it is

carried out by authorized firms that comply with the law and

relevant secondary regulations.

At the same briefing, economic reforms secretary Regis

Dudena said Brazilian law previously defined only two types of

events as eligible for betting: real-world sports events and

online games.

Dudena said prediction markets had sought to present

themselves as financial products by selling derivatives, but in

practice resembled betting.

"This product that was being presented as a security carried

the potentially very destructive features of gambling," Dudena

said.

Presidential chief of staff Miriam Belchior said the

government's move aimed to prevent the consolidation of a new,

unregulated betting market through prediction platforms.

President Luiz Inacio Lula da Silva's administration, which

has regulated and imposed taxes on online betting firms after

years of operating without rules in the country, has said the

spread of gambling has worsened household indebtedness.