The WWF on Thursday raised the alarm over plummeting elephant populations in Mozambique after an aerial survey showed ivory poaching is decimating herds in the country.

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

"The landscape survey of the Quirimbas National Park conducted in late 2013 found that almost half the elephants sighted from the air were carcasses," it said in a statement.

Most were likely killed by ivory poachers, it added, calling for "urgent action and ongoing commitment to combat these illegal activities."

According to the park's administrators, 80 percent of the elephants killed in the northern coastal park are young animals who are less cautious than the adults.

"The ivory market has gone up. Everyone is trying to get ivory," park administrator Chande Baldeu told AFP.

Locals sell the ivory to middlemen for $50 (37 euros) a kilogram -- less than $500 (370 euros) per tusk.

That is still enough to attract new poachers. "Even people who usually do not poach... are trying to get elephants" Baldeu said.

Some who cannot afford guns dig pits and line them with spikes to trap the elephants, he said.

Communities living inside the park are also willing to tell poachers where to find the elephants because the animals destroy their crops.

According to the WWF, "Mozambique has emerged as one of the main places of the slaughter of elephants and ivory transit in Africa and as a profitable warehouse for transit and export of rhino horn for the Asian markets."

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is due to meet in July to discuss the progress countries like Mozambique have made in combating the illegal ivory trade.

The body last year singled out the southern African country as one of the world's worst failures in combating poaching, and threatened it with sanctions.

"The CITES Secretariat has reached out to Mozambique to help it in tackling the problem but has received little by way of response. Governments meet in Geneva next month... but there appears to be little sense of urgency about the problem."

Other NGOs, including Centro Terro Vivo and the Wildlife Conservation Society (WCS) have raised concerns about poaching in Mozambique, and said its elephant herds could be extinct within a decade.

After years of inaction, Mozambique's parliament this April passed new conservation laws meting out long prison sentences and heavy fines to poachers.

Deeper causes of poaching have yet to be tackled, including "weak enforcement, vulnerable borders, corruption, a lack of institutional co-ordination, the existing legal frameworks, human/elephant conflict... and a lack of appreciation for wildlife by the general populace," the WWF said.