Police on the Indonesian holiday island of Bali warned tourists to be on guard Friday after a huge python killed a security guard at a luxury beachfront hotel.

The four-metre snake is still on the loose after the attack early Thursday at the Bali Hyatt, which is in the popular Sanur area but currently closed for renovation.

The security guard, Ambar Arianto Mulyo, spotted the serpent and succeeded in catching it, a police official said.

Mulyo, 59, gripped its head with his right hand and its tail with his left -- but the snake proved too strong, managing to wrap itself around his neck and strangle him.

He was accompanied by friends but they were too terrified to step in and help, Gusti Ngurah Yudistira, the head of the police criminal investigations unit covering the Sanur area, told AFP.

"The victim died on the spot as his neck was crushed and he could not breath," he said.

The snake is still on the loose after a police search of the hotel and its extensive grounds failed to track down the animal, he warned.

"We urge residents and tourists to stay on the alert," Yudistira said, adding the snake may have slithered into a nearby area of thick foliage opposite the hotel.

The deadly attack came at a busy time on Bali, as foreign tourists pack out the island's palm-fringed beaches for the Christmas and New Year holidays.