China's crude oil imports from Iran reached 2.5 million tons (mt) in December 2012, up 43 percent from November, official data show in a clear indication of the ineffectiveness of US-led sanctions against Iran's energy sector.

According to the figures released by China's General Administration of Customs, China's daily crude imports from Iran in December 2012 also rose 3.6 percent compared to December 2011, Bloomberg reported on Monday.

It marks China's biggest crude import from Iran since it won a renewal of exemption from the United States' oil embargo against Iran.

Shanghai-based oil analyst Li Li predicted that China's oil purchase from Iran would reach between 1.7 and 2 mt per month for the first half of 2013.

For the whole 2012, the highest level of China's crude imports from Iran stood at 633,000 barrels per day (bpd).

Industry officials in China attributed the enhancement in Iran's crude oil exports to improvement in shipment.

Iran is currently China's third largest supplier of crude, providing Beijing with roughly 12 percent of its total annual oil consumption.

At the beginning of 2012, the United States and the European Union imposed new sanctions on Iran's oil and financial sectors with the goal of preventing other countries from purchasing Iranian oil and conducting transactions with the Central Bank of Iran.

The sanctions came into force in early summer 2012.

On October 15, 2012, the EU foreign ministers reached an agreement on another round of sanctions against Iran.

The illegal US-engineered sanctions were imposed based on the unfounded allegation that Iran is pursuing non-civilian objectives in its nuclear energy program.

Iran rejects the allegation, arguing that as a committed signatory to the Non-Proliferation Treaty and a member of the International Atomic Energy Agency, it has the right to use nuclear technology for peaceful purposes.