"Good job, president," wrote Matteo Salvini, who leads the populist League party, on Twitter.
The Lombardy politician had earlier wished the Russian president good luck in the vote, describing Putin as "one of the best political men of our time" and sharing a photo of the pair shaking hands.
Salvini has visited Moscow several times and last spring signed a 'collaboration agreement' with the deputy speaker of the Russian parliament, on behalf of Putin's United Russia party. He ran in the March general election as part of a right-wing coalition led by Silvio Berlusconi, who has had a decades-long friendship with Putin and gave the Russian leader a duvet cover with a photo of the pair for his 65th birthday last autumn.
Giorgia Meloni, who leads the junior party in the same coalition, also used social media to congratulate Putin on his victory.
"Congratulations to Vladimir Putin for his fourth election as President of the Russian Federation. The will of the people in this Russian election appears unequivocal," she wrote.
Putin obtained more than 76 percent of the vote, according to official results, though the independent election watchdog (Movement for Defence of Voters' Rights, or 'Golos') reported irregularities ranging from ballot papers being found in ballot boxes before voting started, to obstruction of cameras in polling stations.
After the victory, Putin's campaign spokesperson Andrei Kondrashov credited British Prime Minister Theresa May with the unexpectedly high turnout, saying: "Every time they accuse us of something unfounded, Russia unites."
He was referring to heightened tension between the two countries following a nerve agent attack in the UK, which has left a former Russian spy, his daughter, and a police officer who attended the scene seriously ill in hospital.
In the tweet congratulating Putin, Salvini shared a link to a blog post disputing the idea of Russian involvement in the attack.
While the leaders of the US, France and Germany have joined the UK in saying there is "no plausible alternative explanation" to Russian involvement in the attack, Italy's first official statement on the incident made no mention of Russia.
"We are very worried by the affair of Sergei Skripal, which put many human lives at risk, and we express our strong solidarity with the British government and population," the brief statement issued by the Italian foreign ministry on Thursday evening said.
"The use of a chemical agent banned by international conventions on UK territory is particularly serious. We are following the international debate on the affair with high attention and will offer our support to every action aimed at guaranteeing security and the respect of international law."
Speaking to reporters on Thursday, Alfano said any response to the attack should be based on "verifiable proof".
In a phone call to May on Friday however, Prime Minister Paolo Gentiloni said it was "legitimate" to expect answers from Russia on any possible role in the attack.
Gentiloni confirmed Italy's "full support and solidarity" and agreed on the need for "international co-operation to maintain pressure on Russia", according to a statement from the British government.