China landed two large civilian aircraft on one of its artificial islands in the South China Sea, drawing more protests over the nation's activities in disputed waters, a U.S. defense official briefed on the latest intelligence told Fox News Thursday.

A defense official confirmed that that at least one large civilian Chinese airliner made one of the test flights Wednesday. Photos showed one of the planes to be a China Southern Airlines Airbus A319-115.

The China Daily newspaper reported the planes made the two-hour flight to Fiery Cross Reef from Haikou on the southern island province of Hainan.

This follows a similar test by China on a new runway on one of its contested islands this past weekend using a Cessna, a small civilian aircraft, according to defense officials.

The Pentagon expects these tests of civilian aircraft to culminate in China sending military jets to its man-made islands in the South China Sea.

China's building of seven islands by piling sand on reefs and atolls has been condemned by its neighbors and the U.S., which accused China of raising tensions in an area where six governments maintain overlapping maritime territorial claims.

The U.S. does not recognize the islands and sailed a Navy warship within 12 nautical miles of one of the islands in late October.

In Manila, visiting British Foreign Secretary Philip Hammond said Thursday that freedom of navigation and overflight in the South China Sea was non-negotiable and urged rival governments to avoid provocative steps.

"They are red lines for us," Hammond said, adding that as a major trading nation, Britain expects to continue exercising those rights.

The earlier test flight Saturday drew angry protests from Vietnam, Philippines and Japan.

Vietnamese Foreign Ministry spokesman Le Hai Binh said in a statement that China's action seriously violated Vietnam's sovereignty and demanded China immediately stop and that it respect international law.

Philippine Foreign Secretary Albert del Rosario warned that China may next impose an air defense identification zone above the contested region, as it did over the East China Sea, and said such a move would be "unacceptable."

China has rejected calls for a halt in island construction, saying its claim of sovereignty over the entire area gives it the right to proceed as it wishes. It says the new islands are principally for civilian use but also help defend Chinese sovereignty.

China's robust assertions of its claims have sparked tense exchanges, mainly among China, Vietnam and the Philippines, over long-disputed and potentially oil- or gas-rich offshore territories also claimed by Taiwan, Malaysia and Brunei.

While the U.S. takes no formal position on the various sovereignty claims, it insists that disputes be settled peacefully and that freedom of navigation be maintained in waters through which more than 30 percent of global trade passes.

Fiery Cross Reef is the largest of the seven new islands that in total compose more than 2,000 acres of reclaimed land. Its 10,000-foot airstrip is long enough to handle any plane operated by the Chinese military.

Another runway is being built on Subi Reef, with signs of similar work underway on nearby Mischief Reef. If all are completed, China would possess four airstrips in all on its South China Sea island holdings.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.