Poachers operating in one of Africa’s oldest parks have slaughtered at least 68 elephants in the last two months, using chainsaws and armed helicopter to profit from an illegal trade that results in tens of thousands of deaths every year, conservationists warned.

A report released Friday by the Geneva-based Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) found that at least 20,000 elephants were killed in Africa in 2013 — fewer than the two previous years but still shockingly high.

The Johannesburg-based African Parks group, underscoring the need for greater protection for elephants, said on Thursday that some 4 percent of the population of Garamba National Park in the Democratic Republic of the Congo (DRC) had been wiped out by poachers in a matter of weeks.

The group said that since mid-May, the 1,900-square-mile park, which was established in 1938, has faced an onslaught from several bands of criminals.

One particularly sophisticated group is shooting the elephants with high-powered rifles from a helicopter and then severing their tusks with chainsaws. They are removing the elephants’ brains and genitals as well.

African Parks, which runs seven parks in six countries in cooperation with local authorities, said the poachers include renegade elements of the Congolese army, gunmen from South Sudan and members of the Lord’s Resistance Army (LRA), a militant rebel group whose fugitive leader, Joseph Kony, is an alleged war criminal.

“The situation is extremely serious,” Garamba Park manger Jean-Marc Froment said in a statement. “The park is under attack on all fronts.” A 2012 census found just 2,000 elephants in Garamba — down from 20,000 in the 1960s.

In one skirmish with poachers, park guards had to protect themselves against hand grenades thrown by South Sudanese poachers, some wearing military uniforms.

Conservationists say a thriving ivory market in Asia is helping fuel the worst poaching epidemic of African elephants in decades.

Eighty percent of the African seizures were in Kenya, Tanzania and Uganda, three of the eight nations required to draw up plans to curb ivory smuggling, officials with CITES reported.

The CITES report says poaching is increasing in the Central African Republic but declining in Chad. The report also says the overall poaching numbers in 2013 dropped from the previous two years.

“We are seeing better law enforcement and demand-reduction efforts across multiple countries, as well as greater political and public attention to this unfolding crisis,” said John Scanlon, CITES’ secretary-general.

CITES, which regulates 35,000 species of plants and animals, banned ivory trade in 1989.

About 28 percent of Africa’s elephants are in eastern Africa, and close to 55 percent are in southern Africa. Some local elephant populations continue to face the threat of immediate extinction.

In recent years, the U.N. has warned that armed groups in Africa have been turning to ivory poaching to fund their struggles.

Al Jazeera and The Associated Press