China and Russia have launched eight days of naval drills in the South China Sea in a sign of growing cooperation between the countries' armed forces against the backdrop of regional territorial disputes.

The exercises come at a time of heightened tension in the contested waters after a UN-backed tribunal ruled in July that China did not have historic rights to the South China Sea and criticised its environmental destruction there. China rejected the ruling and refused to participate in the case.

The "Joint Sea-2016" war games will include exercises on "seizing and controlling" islands and shoals, according to Chinese navy spokesman Liang Yang.

They will involve surface ships, submarines, fixed-wing aircraft, ship-borne helicopters, marine corps and amphibious armoured equipment from both navies, he said in a statement on Sunday.

"Compared with previous joint drills, these exercises are deeper and more extensive in terms of organisation, tasks and command."

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The ministry did not say exactly where the drills would be held in the South China Sea, the site of heated territorial disputes between China and its Southeast Asian neighbours.

However, Chinese news agency Xinhua said the Russian ships arrived early on Monday in the Guangdong province port of Zhanjiang, and the exercises would be held off the Guangdong coast, apparently in waters that are not in dispute.

Joint Chinese-Russian drills have become increasingly common in recent years. This week's exercises are the fifth between the two navies since 2012.

China claims most of the South China Sea, through which more than $5 trillion of trade moves annually. Brunei, Malaysia, the Philippines, Taiwan and Vietnam have rival claims.

China has repeatedly blamed the United States for stoking tension in the region through its military patrols, and of taking sides in the dispute.

In July, an arbitration panel in The Hague, Netherlands, issued a ruling invalidating China's claims to virtually the entire South China Sea, a result that Beijing angrily rejected as null and void.

Russia has been a strong backer of China's stance on the arbitration case, which was brought by the Philippines.

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While China says the drills do not envision specific enemies or target any third parties, their location in the South China Sea has drawn criticism.

During a visit to China last month, the commander of the US Pacific Fleet, Scott Swift, said: "There are other places those exercises could have been conducted." He described them as part of a series of actions "that are not increasing the stability within the region".

Xinhua rejected such sentiments in a commentary on Monday, saying those viewing the exercises as threatening were "either ill-informed ... or misled by their prejudice about China and Russia".

Russian news outlets said 18 ships, 21 aircraft and more than 250 marines from both sides would take part in the drills. The ships include destroyers, cruisers, a Russian battleship, amphibious warfare ships and supply vessels.

However, Xinhua said the Russian component would include three surface ships, two supply ships, two helicopters, 96 marines, and amphibious armoured equipment.

China's navy would contribute 10 ships, including destroyers, frigates, amphibious ships, supply vessels and submarines, along with 11 fixed-wing aircraft, eight helicopters, 160 marines and amphibious armour, it said.