* Swiss back 15% minimum business tax

* Minimum tax backed by business groups

* Climate law, rejected in 2021, passes

* Extension to COVID-19 law wins approval

ZURICH, June 18 (Reuters) - Swiss voters voted on Sunday to introduce a global minimum tax on businesses and a climate law that aims to cut fossil fuel use and reach zero emissions by 2050, public broadcaster SRF reported.

The results showed 79% of those who voted in Sunday's national referendum backed raising the country's business tax to the 15% global minimum rate from the current average minimum of 11%, while 59% supported the climate law.

In 2021, Switzerland joined almost 140 countries that signed up to an Organisation for Economic Cooperation and Development (OECD) deal to set a minimum tax rate for big companies, a move aimed at limiting the practice of shifting profits to low tax countries.

Even with the increase, Switzerland will still have one of the lowest corporate tax levels in the world, and the proposal, estimated to bring 2.5 billion Swiss francs ($2.80 billion) per year in additional revenue, has been backed by business groups, most political parties, and the general public.

The climate law, brought back in a modified form after it was rejected in 2021 as too costly, has stirred up more debate with those campaigning against it gaining traction in recent weeks.

Proponents say the law is the minimum the wealthy country needs to do to prove its commitment to fighting climate change while opponents from the right wing People's Party say it will jeopardise energy security.

In Sunday's referendum, voters also approved to extend some provisions of the country's emergency COVID-19 law, required under Switzerland's system of direct democracy, where legislation is put to the public vote.

Switzerland is home to the offices and headquarters of around 2,000 foreign companies, including Google as well as 200 Swiss multinationals, such as Nestle. While all would be affected, business groups have welcomed the greater degree of certainty that the new tax would bring, even if Switzerland lost some of its low-tax allure.

"No other country is going to have lower taxes either. We want the additional tax revenue to stay in the country, and be used to improve its attractiveness for businesses," said Christian Frey, from Economiesuisse, a lobby group. ($1 = 0.8937 Swiss francs)

(Reporting by Noele Illien, John Revill and Emma Farge; Writing by Tomasz Janowski and Noele Illien; Editing by Frances Kerry, Hugh Lawson and Sharon Singleton)