Team UAE rider and Tour de France champion Tadej Pogacar surged through the snow in the Tirreno-Adriatico on Saturday to take the race lead.
The 148km stage from Terni ended with a ferocious battle between a group of elite riders up the 14.7km climb to Prati di Tivo.
The Slovenian held off a late pursuit by defending champion Simon Yates to edge the Briton by six seconds with Colombian Sergio Higuita leading the remainder of the group of contenders home 29 seconds back.
Pogacar took over the race lead from Belgian Wout Van Aert of Jumbo Visma, who limited the damage by finishing ninth, 45 seconds back, after a gritty ride.
"Today I had a battle with myself the last few Ks," Pogacar said at the finish.
"Simon was coming close in the end, but I struggled to the finish. I did everything I could. It was a fast climb. It was a super climb."
The long final ascent was marked by a string of attacks including jabs by the two Ineos former Tour de France winners Egan Bernal and Geraint Thomas.
Pogacar caught Welshman Thomas and then, with 5.6km to go, powered away alone.
"When I went on the attack, I tried to get rid of everyone," said Pogacar. "I tried to be alone and go my own tempo."
Yates, of BikeExchange, finally gave chase, but like his brother Adam of Ineos, who finished second to Pogacar in the UAE Tour last month, could not quite match the Slovene.
The burly Van Aert, who at around 78kg is less well suited to climbing than the wiry mountain men such as Pogacar, refused to be distracted by the sudden accelerations of his rivals.
He slogged up the slope at an unwavering tempo as more natural climbers such as Colombian Bernal, Thomas and French world champion Julian Alaphilippe all cracked.
"I would have liked to hang on longer," Van Aert said. "But Tadej started quite early and that was not in my favour. The pressure was on me and I had to pace for myself. I think I did the best I could. Thirty-five seconds is a nice advantage for Tadej but there are three more stages."