Iran is building a new rocket launch site a short distance from an existing complex and seems to be working with North Korea, information group IHS Jane's said Friday.

Construction visible from satellite imagery of the new site, near the city of Semnan east of Tehran, suggests that Iran has been collaborating with Pyongyang, said the London-based defence intelligence group.

Iran unveiled the Simorgh (Phoenix) space-launch vehicle (SLV) on February 3 but has not publicly revealed the location of the rocket's launch complex, it reported.

But Jane's said it had observed a new launch pad four kilometres (6.5 miles) northeast of the existing Semnan site on a satellite image dated February 6.

The site could ultimately launch Tehran's next-generation Simorgh rocket, it said.

Jane's said that using satellite photographs taken on February 11, as Iran celebrated the Islamic revolution's 31st birthday, it had identified the Simorgh and Safir-2 rockets displayed in Tehran's Azadi Square.

The site includes a gantry tower which is 13 metres (43 feet) wide, approximately 18-20 metres tall "and has a cliff-side flame bucket nearly as high as the tower itself."

"It appears midway towards completion," it said, adding that the launch pad could easily accommodate the 27-metre Simorgh if the gantry were to be extended by an additional 10 metres.

And it added: "The development of the Semnan facility and the Simorgh SLV both demonstrate the likelihood of collaboration with North Korea in Iran's missile programme.

"The platforms seen on the new gantry tower resemble those seen on the gantry tower at North Korea's new launch pad at Tongchang. A drainage pit 170 metres directly in front of the pad also mirrors one at Pyongyang's new west-coast launch site.

"Similarly, the first stage of the Simorgh strongly resembles the North Korean Unha-2, with four clustered engines and nearly the same dimensions."

The respected information group concluded that Iran appears to be forging ahead with developing its missile and rocket capabilities despite US-led diplomatic pressure, including threats of new United Nations sanctions.

"Given these investments in its missile infrastructure, and despite the United States attempting to garner support for further sanctions against Iran for its nuclear programme, Tehran appears determined to continue developing its missile and rocket capabilities in the foreseeable future," it said.

The West suspects Iran of secretly trying to build an atomic bomb and fears the technology used to launch space rockets could be diverted into developing long-range ballistic missiles capable of carrying nuclear warheads.

Tehran denies having military goals for its space programme or its nuclear drive.