HANOI/HONG KONG (Reuters) - Dozens of Chinese naval vessels are exercising this week with an aircraft carrier in a large show of force off Hainan island in the South China Sea, satellite images obtained by Reuters show.

The images, provided by Planet Labs Inc, confirm a Chinese carrier group has entered the vital trade waterway as part of what the Chinese navy earlier described as combat drills that were part of routine annual exercises.

The Liaoning carrier group last week traversed the Taiwan Strait, according to the Taiwanese defense ministry.

The photos, taken on Monday, show what appear to be at least 40 ships and submarines flanking the carrier Liaoning in what some analysts described as an unusually large display of the Chinese military’s growing naval might.

Sailing in a line formation more suited to visual propaganda than hard military maneuvers, the flotilla was headed by what appeared to be submarines, with aircraft above.

Jeffrey Lewis, a security expert at the California-based based Middlebury Institute of Strategic Studies, said the images showed the first confirmation that the carrier was joining the drills.

“It’s an incredible picture,” he said. “That’s the big news to me. Confirmation that, yes, the carrier participated in the exercise.”

Satellite photo dated March 26, 2018 shows Chinese ships south of Hainan, China. Planet Labs/Handout via REUTERS

While the Liaoning has previously entered the South China Sea as part of drills in uncontested training grounds south of Hainan, its annual exercises are closely watched by regional and international powers eyeing Beijing’s growing military might.

It is unclear where the flotilla was headed, or how long operations will last. China’s defense ministry did not immediately respond to a faxed request for comment.

Collin Koh, a security expert at Singapore’s S. Rajaratnam School of International Studies, described the deployment as unusual for its size and scope.

“Judging by the images, it does seem they are keen to show that elements of the South Sea Fleet are able to routinely join up with the carrier strike group from Dalian in the north,” he said.

“It does seem they want to show inter-fleet interoperability - something the (Chinese) navy has been quietly working on for some time.”

Chinese naval and coast guard forces have expanded rapidly in recent years and now patrol the vast swathes of the South China Sea, but little is known about their combat readiness and co-ordination.

Koh said as well as the destroyers, frigates and submarines that would ordinarily support a carrier, the flotilla appeared to include a large oiler for re-supply as well as smaller corvettes and possibly fast attack catamarans.

“While it highlights an extensive ability to deploy, we are still left to guess at the PLAN’s combat readiness,” Koh said.

As well as Vietnam, China’s claims in the South China Sea are disputed by the Philippines, Malaysia and Brunei while Taiwan also has claims.

The exercises come amid fresh signs of tension in the resource-rich waterway, with Vietnam recently halting oil exploration off its coast by Spanish firm Repsol under pressure from Beijing.

Beijing also objected to a so-called freedom of navigation patrol by a U.S. warship last week close to one of its artificial islands in the Spratlys archipelago further south.