China and Russia began eight days of military drills in the South China Sea on Monday.

The internationally contested region is the location of increasing collaboration between the world's second- and third-largest militaries. The exercises will feature so-called "island seizing" activities: anti-submarine operations, fire drills and island defense.

These are largest joint operations in history by the two navies, Chinese navy spokesman Liang Yang said.

"Together, Chinese and Russian participants will undertake defense, rescue, and anti-submarine operations, in addition to joint-island seizing missions and other activities," Liang said Sunday.

China claims 85 percent of the South China Sea's contested waters; Vietnam, Philippines, Malaysia, Brunei and Taiwan have competing claims. China in recent years has begun land reclamation in the disputed area, creating and then weaponizing islands from which it can enhance its claims.

"By holding the exercise with China regardless of the sensitivity of the issue, Russia is effectively showing its support for China," Wang Haiyun, a retired major general previously stationed in Russia, told Financial Times .