VIENNA - The International Atomic Energy Agency (IAEA) said Thursday it has evidence of suspicious activity coming from the Democratic People's Republic of Korea (DPRK)'s Yongbyon nuclear complex that may indicate it is in operation again.

Director General of the IAEA Yukiya Amano told an IAEA Board of Governors meeting in Vienna that satellite photos show signs the reactor may have been re-commissioned into use.

"Activities have been observed at the site that are consistent with an effort to restart the 5MW(e) reactor," he said according to a copy of his speech.

He added this was impossible for the Agency to determine with certainty, however, due to a lack of access to the site which is about 90 kilometers north of Pyongyang, and that he was "seriously concerned" about the potential new development.

The DPRK government has refused the IAEA access to the site since 2009, and stated back in July this year it would not give up its "nuclear deterrent" against Washington.