A Thai elephant gifted to Sri Lanka two decades ago arrived back in its birth country Sunday, following a diplomatic spat over the animal's alleged mistreatment.

Thai authorities had gifted the 29-year-old Muthu Raja -- also known back in its birthplace as Sak Surin -- to Sri Lanka in 2001.

But they demanded the elephant back last year after allegations that it was tortured and neglected while kept at a Buddhist temple.

The 4,000-kilogram (8,800-pound) mammal arrived in Thailand just after 2 pm (0800 GMT), having been transported inside a specially constructed giant steel crate onboard an Ilyushin Il-76 cargo plane.

"He arrived in Chiang Mai perfectly," Thai environment minister Varawut Silpa-archa said at the airport.

"He travelled five hours and nothing is wrong, his condition is normal."

"If everything goes well, we will move him," he added, referring to plans to quarantine the elephant at a nearby nature reserve.

Varawut helped give the elephant a drink after Muthu Raja's decorated crate was removed from the plane, with the thirsty animal eagerly reaching his trunk through a hole to accept the water.

The elephant could be seen when officials briefly opened the crate's rear doors and it was sprayed.

Muthu Raja was moved from its temporary home at a zoo in Sri Lanka's capital Colombo before dawn, accompanied by four Thai handlers and a Sri Lankan keeper, with two CCTV cameras monitoring its health in transit.

It left Colombo at 7:40 am (0210 GMT) on a commercial reparation flight that Thai officials said cost $700,000.

Muthu Raja was in pain and covered in abscesses when it was rescued from the Buddhist temple last year, the zoo's chief veterinarian, Madusha Perera, told AFP.

Animal welfare groups said the elephant had been forced to work with a logging crew and that its wounds, some allegedly inflicted by its handler, had been neglected.

The elephant will undergo hydrotherapy in Thailand to treat a remaining injury on its front left leg, Perera said.

- Return opposed -

Elephants are considered sacred in Sri Lanka and are protected by law.

The organisation Rally for Animal Rights and Environment (RARE), which led a campaign to rescue Muthu Raja from the temple, expressed its unhappiness over the animal's departure.

RARE organised a Buddhist blessing for the elephant on Friday ahead of its journey and has petitioned authorities to prosecute those it says are responsible for neglecting the animal.

Sri Lanka's wildlife minister Pavithra Wanniarachchi said Thailand was "adamant" in its demands for the elephant's return.

Prime Minister Dinesh Gunawardena told parliament in June he had personally conveyed Sri Lanka's regrets to the Thai king over the elephant's condition.

Thailand has stopped sending elephants abroad, Thai environment minister Varawut said, adding that Bangkok's diplomatic missions are checking the conditions of elephants already sent overseas.