By Tommy Lund and Liz Hampton

TESERO, Italy, Feb 20 (Reuters) - When the Varesco family headed off to watch the biathlon at the Winter Olympics on Wednesday they left their two-year-old Czechoslovakian wolfdog ‌Nazgul locked in his kennel at home in Tesero.

In their absence, Nazgul became the most unlikely star ‌of the Milano Cortina Games after escaping from the house and wandering onto the nearby Olympic cross-country course before sprinting down the finishing straight ​alongside the skiers.

"We were on the train to Anterselva to watch the biathlon," Alice Varesco told Reuters on Friday.

"We were three hours from home when friends started sending us videos. That was the panic moment. We realised we could not do anything."

For a few surreal seconds during the qualifying races, spectators thought a wolf had wandered onto the course.

Instead, it ‌was Nazgul, lean and silver-grey, ears pricked, locking ⁠onto the skiers ahead of him and instinctively joining the chase.

He even appeared in an official photo finish image, which was how Alice and Ernesto Varesco ultimately confirmed it was ⁠their dog.

"Concern, for sure," Alice said of her first reaction. "It was with us the whole day actually. Even after they told us he was safe, we kept thinking about what could have gone wrong."

Nazgul had never previously got out of the house ​on ​his own and the Varescos think that, frustrated at being ​left behind, he may have nudged a lever ‌repeatedly until it gave way before managing to get the door to the house open.

"He wanted to look for us I think because he's used ... to going in that direction with us when we go for a walk," Alice said. "He likes to stay with his crew."

NAZGUL CAUGHT INSIDE VENUE

Race officials reacted quickly to the incursion. The race director managed to catch Nazgul inside the venue, and family members brought him home within half an hour.

By early afternoon, ‌the footage had travelled around the world.

"Everyone was sending us videos ​and pictures. At a certain point we just closed the phone because ​it was impossible," Alice added. "We were in Anterselva ​with small kids and we said we need to be here and we'll look at ‌everything later."

Security around Nazgul's kennel has been tightened ​to prevent any repeat for ​the 50-kilometre races this weekend, which the family will watch from the balcony at home with their wolfdog firmly in sight.

The Varescos are most of all relieved that Nazgul's day out did not result in ​any injury or serious disruption.

"We did not ‌think this could be possible, but generally the reaction was people loved him," Alice said.

"And it's ​good that nothing happened and it was going in a positive way, so everybody was happy."

(Tommy ​Lund and Liz Hampton in Tesero; Editing by Nick Mulvenney)