NAIROBI (AFP) - Poachers have killed seven elephants near Kenya's Tsavo National Park over the past month, wildlife officials said Tuesday. The Kenya Wildlife Service (KWS) said the animals died in a migrating corridor near the Kenya-Tanzania border, where seven Tanzanian poachers and their Kenyan guide were arrested over the weekend. "Of the seven elephants, we recovered tusks for only two," Tsavo chief warden Julius Cheptei told AFP. Cheptei said the elephants were killed in the nearby Koranze ranch, which serves as a corridor for the animals when migrating from Tsavo to Tanzania's northeastern Mkomazi Game Reserve. "We suspect that the Tanzanians we arrested over the weekend are part of a syndicate that is notorious for poaching. But we have intensified security in the parks and along the corridors," he added. Poaching slashed Kenya's elephant population from nearly 50,000 in 1965 to about 10,600 in the early 1990s but conservation efforts and anti-poaching measures saw numbers inch back up to 30,000. The state-run KWS said most poachers in southwestern Kenya cross over from Tanzania, where they have nearly wiped out wildlife in Mkomazi Game Reserve. "These incursions could be a result of a lack of wildlife in many parts of Tanzania caused by abused licensed hunting," KWS spokesman Paul Udoto explained. Over the weekend, KWS increased surveillance in the country's animal sanctuaries after 214 of kilograms of zebra and wildebeest meat destined for Nairobi markets were impounded. Last month, the 171-nation Convention on International Trade in Endangered Species (CITES) approved a landmark nine-year ban on international ivory trade to stem a surge in poaching that has killed up to 20,000 elephants per year.