The shooting was the most serious attack on a European leader in decades, drawing shock and condemnation from Slovak officials and other European leaders and stoking fears that Europe’s increasingly polarized and venomous political debates had tipped into violence.

The events were captured on videos, which showed Mr. Fico, 59, approaching a small group of people behind a waist-high metal barrier on a public square in the town of Handlova, when a man stepped forward and fired a pistol from just a few feet away. Five bangs could be heard.

With the first bang, Mr. Fico doubled over at the waist and fell backward onto a bench as more reports ring out. Security officers then hustled him into a black Audi several feet away, half-carrying him to the car’s rear door. He was taken to a local hospital and airlifted to another for surgery.

Security officers at the scene of the shooting wrestled a suspect to the ground, and officials said that initial evidence pointed to political motivations. The authorities did not identify the suspect, whom Slovak news outlets described as a 71-year-old poet. The country’s interior minister, Matus Sutaj Estok, said more information would be made public “in the coming days.”

The president of Slovakia, Zuzana Caputova, whose position is largely ceremonial, said in a statement, “The shooting of the prime minister is first and foremost an attack on a human being, but it’s also an attack on democracy.”

The shooting also drew a chorus of condemnation from world leaders, including President Biden, who called it a “horrific act of violence,” and Russia’s leader, Vladimir V. Putin, who lauded Mr. Fico as a “courageous and strong-minded man.”

Mr. Fico began his three-decade political career as a leftist but over the years shifted to the right, as did the party he founded, Smer. He served as prime minister from 2006 to 2010 and from 2012 to 2018, before returning to power in elections last year. After being ousted amid street protests in 2018, he was re-elected on a platform of social conservatism, nationalism and promises of generous welfare programs.

Mr. Fico presented himself as a pugnacious fighter for the common man and an enemy of liberal elites and immigration from outside Europe, and he aligned with Hungary’s prime minister, Viktor Orban, in opposing aid to Ukraine and challenging mainstream opinions within the European Union.

Domestically, his critics accused him of undermining the independence of the news media, opposed his efforts to restrict foreign funding of civic organizations and called him a threat to democracy. They also accused Mr. Fico of seeking to take Slovakia back to the repressive days of the Soviet bloc.

Here is what else to know:

• Mr. Fico was in Handlova to hold a governmental meeting, which he followed with a nearly hourlong news conference. He had just emerged from those events when he was attacked.

• The Parliament of Slovakia suspended its meetings and said it was “significantly” bolstering its security measures. Some of Mr. Fico’s parliamentary allies suggested that his liberal opponents had created the atmosphere for the shooting.

• Michal Simecka, the chair of the opposition party Progressive Slovakia, said he shared in the “horror” of the attack and stressed that the attacker was not a member of his movement or connected to his party in any way.

Pavol Strba and Gaya Gupta contributed reporting.