Horrified tourists watched as a pack of lions ate a zookeeper alive in Thailand this morning.

The beasts pounced on the worker when he stepped out of his jeep in the open enclosure at Safari World in Bangkok at around 11 am local time.

Shocked visitors screamed as the predators pinned down their victim and feasted on human flesh.

Onlookers, including a number of zoo workers, could only sound their horns in a futile attempt to scare away the sub-Saharan big cats.

Officials arrived with guns, which caused the lions to scatter, but the zookeeper was already mauled to death as the lions gnawed his body until the bones were exposed.