[ Photo above: AFP/File - Handout from the Royal Children's Hospital shows conjoined twins Krishna (left) and Trishna. ]

MELBOURNE (AFP) - A pair of Bangladeshi twins who are joined at the head will undergo a risky and highly complex operation to separate them next week, Australian surgeons said on Friday.

Trishna and Krishna, now almost three years old, have undergone a series of delicate operations to separate the blood flow to their brains since a charity first brought them to Australia two years ago.

A team of 16 specialists will work for 16 hours from early morning until midnight to part the pair in Melbourne on Monday, in what lead surgeon Wirginia Maixner said was a high-stakes procedure.

"We gave the odds of one in four chances of the girls dying and one in two chances of them coming through but having a significant deficit," Maixner told state radio.

"There is always a risk that something could happen, either or both twins could die," she added.

Doctors would separate the section of brain and remaining blood supply connecting the twins as well as a small amount of bone and skin, with a risk of "serious brain injury" were things to go wrong, she said.

"We have a team of plastic surgeons who will then replace bone that's missing and close the skin over the top," Maixner said.

Krishna had been "at death's door" when the twins arrived in Australia but Maixner said despite kidney troubles she and her twin were now thriving, and doctors were optimistic of a good outcome.

"They're quite dramatically better than when we first met them. They're really robust and so we've already made a significant difference," she said.

"I think the chances now are well in our favour that we can get them through it."

The Children First Foundation (CFF) flew the girls to Australia in January 2008 because of poor separation survival rates in their native Bangladesh.

Four previous operations in Bangladesh to separate conjoined twins in the past few years have resulted in the deaths of all but two children.

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