SAN MARTINO DI CASTROZZA, Italy -- Italy's Danilo Di Luca won the fourth stage of the Giro d'Italia in an uphill finish Tuesday while Lance Armstrong finished 15 seconds behind and dropped to sixth place overall.
Sweden's Thomas Lovkvist of Team Columbia-High Road was seventh and took the overall leader's pink jersey from Alessandro Petacchi of Italy. Lovkvist holds a two-second lead over Di Luca in the overall standings.
Armstrong is recovering from a broken collarbone in March and competing in this race for the first time. The seven time Tour de France champion entered the day in fifth place and is 28 seconds behind Lovkvist.
"I'm happy with my performance today. This was my first big climb since retiring," Armstrong said in a statement released by his Astana team. "I had a good feeling and no collarbone pain at all."
Armstrong is returning this year after 3½ years of retirement. He said the 15 seconds he lost was "not much," adding that he needed to adjust his gears at one point.
"Of course, it was not a very difficult climb," he said. "Tomorrow will be a better indication. It will be a long and hard day. We'll see. I don't know what to expect."
Wednesday's arduous mountain stage is from San Martino to Alpe di Siusi. The race ends May 31 in Rome.
Di Luca, the 2007 Giro winner, dedicated the victory to his Abruzzo region. The area was hit by an earthquake early last month that killed nearly 300 people and drove some 50,000 from their homes.
"I wanted to win for my territory today," said Di Luca, who twisted his body as he crossed the line to show the words printed on the side of his jersey -- "Forza Abruzzo" or "Go Abruzzo."
Di Luca, who rides for the LPR Brakes team, covered the 101-mile leg from Padua to San Martino di Castrozza in the Dolomite range in 4 hours, 15 minutes, 4 seconds.
He was followed by Stefano Garzelli and Franco Pellizotti -- both in the same time as the winner -- to give Italy a podium sweep.
Armstrong lost contact with the leaders in the final mile and declined to speak with reporters in the finish area. Sweating profusely and looking exhausted, he was not happy after the stage when his handlers could not immediately give him a cold drink.
"Come on, guys," he said.
Armstrong said before the race he would ride in support of Astana teammate Levi Leipheimer. Leipheimer was sixth Tuesday with the same time as Di Luca; Armstrong was 32nd. The other race favorites finished in the lead pack.
"Lance looked really good all day," said Astana team member Chris Horner, dismissing the amount of time Armstrong lost. "That's really small."
Leipheimer is fifth overall, 26 seconds behind Lovkvist. Overall race favorite Ivan Basso is 11th, 53 seconds back.
"Levi looks fantastic as always -- real smooth," Horner said. "I don't think you'll see a whole lot of action from our team until you get a little further into the race."
Di Luca and the other top Italians want to take time from Armstrong before the two individual time trials later in the race.
"We're trying to cut him out completely," Di Luca said. "It's tough, but we're going to try again tomorrow. It's going to be a very competitive Giro. This first week is very important for me, because the time trial doesn't suit me."
Petacchi, who also rides for LPR, won the past two stages in sprints. Team Columbia's Mark Cavendish wore the pink jersey after the first two stages.
"I had very good legs," Lovkvist said. "We got the jersey back for the team again and we're not going to give anything away."
Spain's Francisco Perez Sanchez of the Caisse d'Epargne team fell seven miles into the stage and was put on a stretcher and taken to a hospital. Details of his injuries were not immediately available.
The day's first significant climb came after 69 miles -- a 5.3-mile ascent to Croce d'Aune. The road then began to tilt upward again after 92 miles.
Six riders -- Francesco Bellotti, Davide Vigano, Ian Stannard, Francesco De Bonis, Jens Voigt and Serafin Martinez Acevedo -- broke away from the pack early and established a seven-minute lead at one point. Voigt, the last remnant of the breakaway, was caught with 1.5 miles to go.