Elephant poaching is happening on an unprecedented and “industrialised” scale in Mozambique, environmentalists have warned, after 22 of the animals were killed for their tusks in the first two weeks of September.

The Wildlife Conservation Society (WCS) said organised crime syndicates are slaughtering between 1,500 and 1,800 elephants a year in the southern African country, feeding demand for ivory in the far east. There are fears that Mozambique’s elephant herds could be extinct within a decade.

The crisis, described by the WCS as a “national disaster”, was discussed during a two-day meeting of Mozambican officials, law enforcement agents and diplomats in the capital, Maputo.

Carlos Pareira, an adviser to the New York-based WCS, told the seminar of the worsening situation in Niassa, the country’s biggest game reserve, where “in the first two weeks of September alone we counted 22 elephants that had been killed.”

The Niassa reserve, co-managed by the WCS with the Mozambican authorities, is double the size of South Africa’s popular Kruger national park. Pareira added: “The killing of elephants in the north of Mozambique … is reaching proportions never seen before. The killing of elephants is being industrialised.”

Poachers use automatic weapons and high-calibre hunting rifles to kill the animals, the meeting heard. In the northern Tete province, they poison drinking water sources, killing not only elephants, while spikes concealed in the bush have also been used to wound animals in the coastal Querimbas reserve, causing them slow and agonising deaths from gangrene.

Between 480 and 900 elephants died in the Querimbas between 2011 and 2013, according to a recent aerial study commissioned by the WWF.

Ivory from Mozambique has been traced to markets in Hong Kong and Taiwan, but trinkets and carvings are also sold at craft markets in Maputo, the meeting heard.

Mozambique has previously been criticised by the Convention on International Trade in Endangered Species as one of the world’s worst failures in combating poaching and threatened with sanctions. Poaching was not considered a crime until recently, and anyone arrested often got off with a fine for illegal weapons possession.

A new law passed in June toughens penalties for poaching, including hefty fines and jail terms of up to 12 years for killing protected species. Although the new conservation law was approved in June, it will only go into effect at the end of the year, officials said.

Douglas Griffiths, the US ambassador to Mozambique, described the law as a “crucial step”, but said the government would need to “ensure it is respected by all and fully implemented”.

An estimated 25,000 elephants are killed every year in Africa for their tusks, double the number killed in 2007. A global march demanding action to stop elephant and rhino poaching will be held across 125 cities on 4 October.