Russia's Natural Resources Ministry has revoked its approval for Royal Dutch Shell's $20 billion Sakhalin-2 oil and gas project.

The move by the Russian ministry follows weeks of uncertainty amid tussles between Shell and the ministry over ecological compliance issues.

It also follows news that Russia’s Prosecutor General’s Office and the Natural Resources Ministry recently concluded that the original permit issued for the second phase of the project should not have gained approval.

However, a ministry spokesperson is reported to have stated that the decision may only be a temporary one, and Shell could have its permit reinstated within six months.

Nevertheless, the annulment has begun stirring speculation that the ministry’s move is a bid to put pressure on Shell to conclude a deal with Gazprom, which wants to gain a stake in the Sakhalin-2 project.

It has also been reported that the Russian authority is considering revoking similar permits for Exxon Mobil and Total.