PHNOM PENH - Cambodia has banned all sand exports on environmental grounds, the Ministry of Mines and Energy said on Wednesday, officially ending the sale of sand to Singapore which has for years used it to reclaim land along its coasts.

The ministry said most of Cambodia's sand had gone towards the expansion of the island city-state of Singapore, and it would now have to look for other sources.

Environmental groups have been pressing the government to stop the trade, saying the digging and dredging of sand has had a serious impact on coastal ecosystems and surrounding land.

Groups have complained that sand in recent months has been exported illegally following a temporary ban in November 2016.

A ministry spokesman, Meng Saktheara, said the government was responding to the concerns of the campaigners and it also agreed that large-scale sand mining was indeed damaging.

"Their worries are right that the risks are massive so the ministry decided to ban sand exports and large-scale sand dredging," Meng Saktheara told Reuters.

Meng Saktheara said Singapore was Cambodia's top market for sand until last year when the temporary ban came into force, and had it imported some 16 million tons of sand since 2007.

U.N. trade data released last year showed that Singapore had imported more than 72 million tons of sand, worth more than $740 million, from Cambodia since 2007.

It was not clear why there was such a big difference between the official government figure for exports to Singapore since 2007 and the U.N. figure.

Singapore's embassy in Phnom Penh did not immediately respond to a request for comment.

Some environmental groups remained skeptical about the ban being properly enforced.

"Sand is being dredged ... are we sure that sand is not being exported?" asked Lim Kimsor, an activist with the group Mother Nature.