"Although it is an approximate date, we hope that if everything goes to schedule, we could witness the plant being connected to the national grid in mid-February," Atomic Energy Organization of Iran (AEOI) Chief Ali Akbar Salehi said after visiting the plant.

Iran started injecting fuel into the core of its first nuclear reactor at the Bushehr nuclear power plant on Tuesday, local media said.

"Today is an auspicious day and a turning point in the process of the Bushehr nuclear plant launch, which means that the most sensitive process (injecting fuel into the core of Bushehr reactor) has started," Salehi said.

The Bushehr plant in southern Iran was launched in August with Russian assistance after decades of construction delays.

Under a bilateral agreement, which has received IAEA approval, Russia will initially operate the plant, supplying its fuel and taking away all the spent fuel for the next two or three years, but will eventually hand over full control to Iran.

Iran remains a target of criticism and sanctions over its controversial nuclear program, which the West claims could be an attempt to build a nuclear weapon.

However, as a member of the International Atomic Energy Agency and a signatory to the Nuclear Non-Proliferation Treaty, Tehran insists its nuclear program is aimed at electricity generation and medical research.

The UN Security Council has approved four rounds of sanctions against Iran over its nuclear program, including tougher financial controls and an expanded arms embargo, as well as an asset ban on three dozen companies and a travel freeze on individuals.

The Bushehr project does not fall under these sanctions.