Korean War Museum
A visitor walks past North Korea's Russian made Scud-B missile and South Korea's U.S. made Hawk surface-to-air missiles at the Korean War Memorial Museum in Seoul REUTERS

North Korea appears to be upgrading one of its two major missile launch sites, supposedly to test bigger rockets, a U.S.-based research institute said Thursday.

North Korea has made significant progress since October in constructing a new launch pad and other facilities at Tonghae, on the country's northeast coast, according to an analysis from 38 North, the website of the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies in Baltimore.

The assessment is based on commercial satellite images that dating back to August last year and continuing into January 2013.

“Imagery of the new launch pad and support buildings indicates that Pyongyang will be able to test rockets perhaps three to four times the size of the Unha when construction is completed, possibly in 2016, depending on the pace of construction,” the report said.

Some design features and activities around the new launch pad had revealed the possible evidence of assistance from Iran, the analysis said.

“A new flame trench covering to protect large rockets from exhaust gases is similar to the covering used at a new launch pad at the Semnan Launch Complex in Iran,” the report noted. “Also, propellant conduits under construction for the new launch pad and rocket engine test stand are similar to those built at Semnan.”

Pyongyang’s nuclear test this week has directed the world’s attention to Iran, which has allegedly been pursuing a clandestine nuclear weapons program despite strong opposition from several world powers, including the U.S.

"This is about proliferation and this is also about Iran ... because they're linked. You connect the dots," U.S. Secretary of State John Kerry said Wednesday at a joint press briefing with his Jordanian counterpart, Nasser Judeh, at the State Department.

"It is important for the world to have credibility with respect to our nonproliferation efforts," he added.

North Korea conducted its third nuclear test on Tuesday. It claimed to have successfully detonated a smaller but more advanced device than those used in the previous tests conducted in 2006 and 2009.

In December, Pyongyang successfully used a three-stage rocket to launch a satellite into orbit. The Sohae test facility was used for the launch.

Meanwhile, South Korea’s outgoing President Lee Myung-bak warned that North Korea would undermine its own regime if it continued to build weapons at the risk of exhausting its already scarce resources.

"If North Korea continues to waste its budget on developing military weapons, it will become difficult to maintain its regime," Lee was quoted as saying on Friday by presidential spokeswoman Lee Mi-yon, according to a report by Seoul’s Yonhap news agency.