MOSCOW -- Russian scientists said Thursday that an effort to put nearly 100 illegally captured whales back in open water has been successful so far, but some environmentalists claimed it was badly organized.

The condition of 97 belugas and orcas kept in cramped conditions in Russia's far east has drawn international concern, and President Vladimir Putin has personally ordered authorities to investigate the case and release the animals.

The first group was released into the Sea of Okhotsk last week. Deputy Prime Minister Alexei Gordeyev told Putin Wednesday the whales have since fully readapted to a natural habitat.

Greenpeace Russia co-ordinator Oganes Targulyan said Thursday he thinks the marine mammals should have spent some time in temporary enclosures before they were let into the open sea.

Targulyan said moving the whales on trucks inside water tanks meant unnecessary risk, arguing that it would be preferable to move them on ships instead.

Scientists with Russian Federal Research Institute of Fisheries and Oceanography rejected the criticism, saying that all due precautions were taken to release the first two orcas and six belugas. They insisted the whales have been safe.

It took 10 days to move the animals from a marine container facility near the port of Nakhodka to an area where they could be safely let closer to the waters where they had lived. The effort involved experts from the institute staying with the mammals in water tanks during transportation to keep them as comfortable and safe as possible.

"Nobody in the world has had experience in massive release of whales," said Vyacheslav Bizikov, a deputy director of Russian Federal Research Institute of Fisheries and Oceanography.

Bizikov said another batch of whales will follow suit next week.