TEHRAN -- Iran has removed the core of its Arak heavy water reactor as the major step toward removal of international and Western sanctions against the country, the spokesman of Atomic Energy Organisation of Iran Behrouz Kamalvandi said on Thursday.

The core of the reactor was removed on Wednesday and the holes of the central part of the reactor were filled with concrete, Kamalvandi told state IRIB TV.

The inspectors of the International Atomic Energy Agency (IAEA), who are currently in Iran, will start the verification process on Thursday, he said, adding that the "implementation" of the Joint Comprehensive Plan of Action (JCPOA) will begin soon.

With the implementation of the JCPOA, "the oppressive sanctions will be removed and we will witness good economic era," he said.

On Wednesday, Iran announced that it has unassembled a significant number of its uranium enrichment centrifuges.