A U.S. Navy ship has sailed close to artificial islands built by China in the disputed waters of the South China Sea, U.S. defence officials have said, according to Reuters.

Guided-missile destroyer USS Lassen breached the 12-nautical mile zone China claims around Subi and Mischief reefs in the Spratly archipelago.

The freedom of navigation operation represents a serious challenge to China's territorial claims.

China said it was still verifying whether the operation had taken place.

"If true, we advise the U.S. to think again and before acting, not act blindly or make trouble out of nothing," Foreign Minister Wang Yi said.

China claims most of the South and East China seas. Other countries in South East Asia have competing claims for the Spratly Islands, Paracel Islands and Scarborough Shoal, which are thought to have resource-rich waters around them.

The reefs, which were submerged, were turned into islands by China by a massive dredging project which began in late 2013.

China says this work is legal and in a meeting with U.S. President Barack Obama last month in Washington, President Xi Jinping said China had "no intention to militarise" the islands.

But Washington believes Beijing is constructing military facilities, designed to reinforce its disputed claim to most of the region - a major shipping zone.