Four dogs - 'well-fed and trained to kill' - hunted down and killed six protected deer in a zoo in China's Yunnan province, officials said Friday.

The dogs got into the zoo and killed four spotted deer and two fallow deer. Another two deer and an emu were injured, Tang Yangchun, head of the Yunnan Wildlife Zoo's animal management department, was quoted as saying by Xinhua.

Tang said some miscreants might have been behind the attack.

'The gates are guarded round the clock. And the dogs couldn't have climbed over the 2.5-metre zoo fence by themselves,' he said.

The dogs, which were later captured and killed by zoo workers, seemed well-fed and trained to kill, he said.