Kenyan wildlife rangers on Tuesday were tracking a team of poachers who massacred a family of 11 elephants in what they said was the worst single such killings in the country in the past three decades.

"We have not lost as many elephants in a single incident since the early 1980s," said Patrick Omondi, head of the elephant programme at the Kenya Wildlife Service (KWS). "This is a clear signal that things are getting worse."

The bullet-riddled corpses of the elephants -- all with their tusks hacked off, and including a two-month old baby -- were found Saturday in south-eastern Kenya's vast Tsavo East National Park.

"Our initial investigations show that the poachers numbered at least 10 and were armed with an assortment of guns," Omondi said, adding that the normal weapon of choice for poachers is an AK-47 assault rifle.

Rangers were tracking the poachers in "hot pursuit" but had so far not caught the gang, KWS said.

Officials say that an increase in demand for ivory in Asia -- where elephant tusks are used in traditional medicines and to make ornaments -- has led to a substantial increase in the killing of elephants in Africa.

"A kilogramme of ivory can fetch up to $2,500 in the black market, money that comes back to fund extremely organised gangs with sophisticated weapons," said Omondi.

In 2012, Kenya lost approximately 360 elephants to poaching, a figure that rose from 289 the previous year, KWS said. At least 40 poachers were killed last year as rangers battled the raiders.

The international trade in elephant ivory, with rare exceptions, has been outlawed since 1989 after elephant populations in Africa dropped from millions in the mid-20th century to some 600,000 by the end of the 1980s.

Last week officials in Hong Kong seized more than a tonne of ivory worth about $1.4 million in a shipment from Kenya.

Ivory trade is banned under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which is due to hold its next meeting in March, a date that Omondi says has in the past triggered a rise in poaching.

As the conference approaches, "countries with elephant herds register a surge in poaching... speculators stockpile the contraband with the hope that the conference will lift the ban on ivory trade," he said.

Africa is home to an estimated 472,000 elephants whose survival is threatened by poaching and habitat loss.