The orer to halt construction had been issued by the Consumer Protection and Technical Regulatory Authority (TTJA).

"Based on the materials forwarded to us by the TTJA, the PPA imposed a prohibition on stay at Aidu Wind Farm from today through 22 April," spokespeople for the PPA told Postimees.

According to TTJA spokesperson Anne-Mai Helemäe, construction work at the wind farm continued on Friday despite the order issued to the developer and the warning of a fine.

"The TTJA has been monitoring the situation, and the state of play we recorded today demonstrated that continuation of the construction activity would entail irreversible damage," Ms Helemäe explained.

The TTJA on 12 April issued an order to halt construction activity at the wind farm, which was physically delivered to the wind farm by a TTJA official on 16 April.

The primary reason for the issuance of the order is an assessment according to which the construction of the wind farm would pose a threat to national security.

The Ministry of Defence has previously said that building large wind turbines in the area in question in Northeastern Estonia would interfere with the operation of military radars.

"The TTJA is also of the opinion that construction activity by the developer is illegal as the developer of Aidu Wind Farm does not have a valid construction permit," spokespeople for the authority have previously said. "The party to which the order was issued is Eleon Green OÜ as the holder of building rights for the Aidu wind farm."

Eleon AS board member Oleg Sõnajalg has described the TTJA's demand to immediately halt development as an unprecedented and brutal move, as the company, according to repeated assertions by the local municipality, "possesses all the permits and rights for putting up its wind turbines."