Customs officers in southern China seized a cannonball tree fruit - which they said could "potentially explode" - from a traveller who was returning from Singapore earlier this month.

The 30cm-wide brown fruit, which resembles a husked coconut and weighs 3.8kg, was tucked inside a luggage bag before it was picked up during X-ray security scanning on Jan 5 at the Gongbei Customs in Zhuhai, Guangdong, according to gd.chinanews.com, the Guangdong news site of China News Service.

The website called the cannonball tree fruit the "world's most dangerous fruit".

The authority said the fruit is a risk as it could "explode" when it is ripe or encounter external force.

The traveller, who did not declare the fruit as required under quarantine and customs regulations, said the cannonball tree fruit was a gift from a friend in Singapore who had planted it. As the fruit was rare, the traveller had planned to enjoy it at home with family.

Gongbei Customs warned that travellers are not allowed to bring fresh fruits and plants which can reproduce into the country, an offence punishable by a fine of not more than 5,000 yuan (S$1,000).

According to the website of Singapore's National Parks Board (NParks), the cannonball tree "was grown for its interesting botanical features and also as an ornamental tree in the Singapore Botanic Gardens". It can also be found elsewhere in Singapore, including the East Coast Park and residential areas.

The red-and-yellow flowers, which are fleshy with a strong sweet scent, are used by Hindus in Singapore for worship.

But the fruit, which hangs along long thick stalks which stick out from the trunk, is filled with notoriously stinky soft red pulp. It takes a year for the fruit to mature, before it comes crashing down to the ground and bursting open with an ear-splitting thud.

The stench of the fruit was once described by gardening author David The Good as "a bloated two-tonne three-day-dead possum passed gas, causing a tequila-saturated hobo to projectile vomit into an adjacent dumpster filled with rotting cheese and mayonnaise".