Thousands of people have already contributed 575,000 euros ($610,000) since Monday, when the "Peace for Ukraine" group launched the initiative, organisers said.

Since coming to power last year, Prime Minister Robert Fico has stopped military aid to Ukraine and advocated for peace talks with Russia.

"We, the residents of Slovakia, want to and can help," said Zuzana Izsakova, a representative of the fundraising initiative.

"We want to show that it is not only the government and Robert Fico who decide on this matter," she told AFP.

The organisation plans to funnel any money raised to an international initiative spearheaded by the Czech Republic to buy ammunition for Ukraine.

The Czech prime minister said Tuesday that 20 countries had pledged enough to buy 500,000 artillery shells for Ukraine outside Europe.

The Slovak government has not joined the initiative.

Marian Kulich, another representative of "Peace for Ukraine", said the project was born out of opposition to the government's stance on Ukraine.

"We are convinced that many people in Slovakia do not identify with the rejection of the Czech government's initiative," Kulich told AFP.

Izsakova said the group's wanted to match the one-million-euro ($1.05 million) donated by the Slovenian government last month.

One notable supporter of the Slovak crowdfunding campaign is Holocaust survivor Otto Simko, who said his own wartime experiences could be applied to events in Ukraine.

The 99-year-old former journalist took part in the 1942 Slovak National Uprising, an attempt to resist German troops during World War II.

"We fought the aggressor, the German occupation... It was impossible to negotiate with them, they had to be defeated," Simko said in a campaign video for the ammunition initiative.

"If I can only give 20 euros to buy one single bullet, I will know that this bullet is in the right hands," he added.