A United States aircraft carrier strike group has begun what the US Navy called “routine patrols” in the South China Sea days after China warned Washington against challenging its sovereignty in the disputes waters.

The US Navy said the strike group, including Nimitz-class aircraft carrier USS Carl Vinson, began patrolling operations in the South China Sea on Saturday.

The group’s commander, Rear Admiral James Kilby, said the effectiveness and readiness of his force had been improved following weeks of training in the Pacific.

"We are looking forward to demonstrating those capabilities while building upon existing strong relationships with our allies, partners and friends in the Indo-Asia-Pacific region," Kilby was quoted as saying by the Navy News Service.

China claims most of the strategic waterway, through which $5 trillion in trade passes annually. The Philippines, Vietnam, Malaysia, Taiwan and Brunei also have overlapping claims with Beijing.

US Navy officials announced a week ago that they were considering sailing more warships near China’s man-made islands in the contested waters.

Tensions between the US and China over trade and territory have increased since President Donald Trump took office, raising concerns that the tense South China Sea could become a flashpoint.

Responding to reports of more US naval patrols, China's Foreign Ministry warned Washington on Wednesday against any military activities in the area.

"We urge the US not to take any actions that challenge China's sovereignty and security," Geng Shuang, the ministry’s spokesman, said at a press conference.

The US last conducted what it called a “freedom of navigation” operation in the South China Sea in October, which included patrols by the guided-missile destroyer USS Decatur, near the Paracel Islands and in waters claimed by Beijing.

China says Washington is meddling in the regional issues and is deliberately escalating the situation in the waters.

China wrapped up its own war games in the South China Sea on Friday. Naval exercises involving an aircraft carrier further rattled neighbors that have been embroiled in long-running territorial disputes with Beijing.