A large segment of a Chinese rocket re-entered the Earth's atmosphere and disintegrated over the Indian Ocean on Sunday, the Chinese space agency said, following fevered speculation over where the 18-tonne object would come down.

Officials in Beijing had said there was little risk from the freefalling segment of the Long March-5B rocket, which had launched the first module of China's new space station into Earth orbit on April 29.

But the US space agency NASA and some experts said China had behaved irresponsibly, as an uncontrolled re-entry of such a large object risked damage and casualties.

"After monitoring and analysis, at ดาวน์โหลดjoker the last-stage wreckage of the Long March 5B Yao-2 launch vehicle has re-entered the atmosphere," the China Manned Space Engineering Office said in a statement, providing coordinates for a point in the Indian Ocean near the Maldives.

It added that most of the segment disintegrated and was destroyed during descent.

The US military's Space Command said the rocket "re-entered over the Arabian Peninsula at approximately 10:15 pm EDT on May 8 (0215 GMT Sunday)".

"It is unknown if the debris impacted land or water."

Monitoring service Space-Track, which uses US military data, said that the location in Saudi Arabia was where American systems last recorded it.

"Operators confirm that the rocket actually went into the Indian Ocean north of the Maldives," it tweeted.

The segment's descent matched expert predictions that any debris would have splashed down into the ocean, given that 70 percent of the planet is covered by water.

Because it was an uncontrolled descent, there was widespread public interest and speculation about where the debris would land.