Chinese cruise ships will regularly bring tourists to the contested Spratly Islands in the South China Sea by 2020, according to Chinese media.

Tensions have been high in the region as Beijing asserts sovereignty over almost all of the strategically vital South China Sea, despite rival claims from its Southeast Asian neighbours.

The China Daily, which is published by the government, said on Wednesday that a new proposal seeks to develop routes to the Spratlys, citing a document released by authorities in the southern island province of Hainan, from where the ships will depart.

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"The Nansha Islands are virgin territory for China's tourism industry," provincial tourism official Sun Xiangtao told the newspaper, using the Spratlys' Chinese name.

Vietnam, Malaysia, Taiwan, Brunei and the Philippines all have rival claims over portions of the Spratlys.

Cruises to Paracels

Chinese tourists have been allowed to travel to non-militarised areas of the South China Sea since 2013, but foreign passport holders are not allowed to join the trips.

Companies have already been operating cruises to the disputed Paracel Islands further north for Chinese nationals only.

A previous China Daily report said that the mayor of Sansha city, on Woody Island in the Paracels, estimated that some 30,000 people have already visited the islands, and "many people with a patriotic spirit want to try it".

Competing claims to the South China Sea, which covers more than three million square kilometres, have for decades been a source of tension in the region.

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The sea is the main maritime link between the Pacific and Indian oceans, giving it enormous trade and military value. More than $5 trillion in ship-borne trade passes through the sea each year.

Major unexploited oil and natural gas deposits are believed to lie under the seabed.

The sea is also home to some of the world's biggest coral reefs and, with marine life being depleted close to coasts, it is important as a source of fish to feed growing populations.