Investigations by European nations, including Denmark, through whose waters the pipeline travels, and Germany, have yet to yield conclusive results.
Putin voiced regret that Russia has been denied access to the materials of the probe. He added the Russian Gazprom natural gas giant has sent a vessel to check the seabed near the explosion and spotted what appeared to be an antenna near a junction between the pipes about 30km (16 nautical miles) from the explosion site.
Putin alleged the antenna could have been put on the seabed to trigger another explosive device that did not detonate for a reason that remains unclear. He added Russia expects Danish authorities to form a joint team to thoroughly check the area.