Russian President Vladimir Putin said Wednesday that Greenpeace activists apprehended after trying to scale an offshore oil platform aren’t pirates, but defended the detention saying Coast Guard officers had no way of knowing who they were.

Two members of the group were detained Sept. 18 in their attempt to scale the Arctic platform. The Coast Guard seized Greenpeace’s ship the next day and towed it with 30 activists aboard, to Murmansk, where they are being questioned by investigators considering piracy charges.

It was unclear whether Putin’s comments might foreshadow leniency for the activists, who could face 10-15 years in prison if convicted of piracy.

The detained activists are from 18 countries, including Russia, and a long detention or trials could draw unwelcome international attention to Russia’s tough policy against protests.

Greenpeace insisted that under international law Russia had no right to board its ship and has no grounds to charge its activists with piracy.