STOCKHOLM — A gang of thieves on Friday staged a remarkable break-in near the Swedish royal family's residence in Stockholm, smashing display cases at a historic 18th-century Chinese-style landmark and getting away with artifacts that police called potentially priceless.

The heist at the ornate Chinese Pavilion, a birthday gift from King Adolf Fredrik to Queen Lovisa Ulrika in 1753, took just six minutes, and occurred just after security guards had made their rounds at 2 a.m., police spokeswoman Diana Sundin said.

"The alarm went off just as the guards had passed by," she said. Guards immediately returned to the scene, but the burglars had already vanished, she said.

The burglars are believed to have entered the building by smashing the glass on the pavilion's back door. Once inside, they shattered three display cases, she said, and made off with an unknown number of "old, beautiful Chinese objects."

"It might not even be possible to put a value on these objects. That's how bad it is," she said. She could not say specifically what was stolen, but the pavilion is known for its display of Chinese artifacts including porcelain, China and vases.

The original small wooden Chinese pleasure palace was replaced by a more robust structure in the 1760s and has rich, European rococo interiors along with its collection of chinoiserie. It is located near the royal family's permanent residence in the Drottningholm Palace park in western Stockholm. Both are on UNESCO's World Heritage List.

Sundin said there are currently no suspects in the case, but that there are indications that there were at least three people involved in the burglary.

She also said police are investigating a motor bike found abandoned in the nearby waterfront that borders the majestic park.

"Right now, everything points toward them having left via the water," Sundin said, adding they may have had a boat waiting for them as they fled the scene.