New construction or excavation is under way at North Korea's main nuclear reactor, near the site of a cooling tower destroyed in 2008, a private US research institute has said, citing a satellite photo.

The Washington-based Institute for Science and International Security (ISIS) said on its website (isis-online.org) that tracks made by heavy machinery and construction or excavation equipment were visible in the photo.

ISIS said there appeared to be ongoing construction of two small buildings next to the site of the cooling tower at Yongbyon -- which the North blew up in June 2008 in front of foreign media to dramatise its commitment to nuclear disarmament.

"It is unclear if the activity seen in this image represents preparation for construction of a new cooling tower or preparation for construction of other buildings or structures for some other purposes," it said in a post dated Thursday.

The new activity appears more extensive than would be expected for rebuilding the cooling tower, but its actual purpose cannot be determined from the image and bears watching, ISIS said.

It said the image, taken on Wednesday, was obtained from DigitalGlobe, an imagery and information company.

Yongbyon, 100 km (62 miles) north of Pyongyang, was the source of plutonium for the North's atomic weapons programme. Its stockpile is believed to be enough to build six to eight bombs.

The North shut down the reactor in July 2007 under a six-nation aid-for-disarmament accord. The following summer, it destroyed the cooling tower as part of work to disable its facilities.

The United States contributed 2.5 million dollars towards the demolition cost.

But six-party talks bogged down in December 2008 over ways to verify the North's work to put its facilities out of action. In April 2009 Pyongyang abandoned the talks and said it had resumed reprocessing spent fuel roads to make weapons-grade plutonium.

In May 2009 it conducted an atomic weapons test, its second.

The North has indicated willingness in principle to return to the six-party talks chaired by its ally China. But it says it wants separate talks with the United States about signing a permanent peace treaty on the peninsula.

South Korea and the United States, which accuse the North of a deadly March attack on a South Korean warship, have responded warily. Japan and Russia are also members of the forum.

earlier related report
High-tech revolution yet to hit North Korea
Pyongyang (AFP) Oct 2, 2010 - Stressed out by email overload and non-stop mobile calls? You might consider a vacation in North Korea, where your cell phone is seized at the airport and Internet is unavailable.

The communist country is one of the world's most tightly-controlled societies and bans unauthorised mobile phones as part of a crackdown on information from outside the country.

Visitors landing at Pyongyang's airport find there is no cellular phone signal. But it does not matter because polite and efficient customs officials confiscate foreigners' phones and put them in a green cloth bag.

They are returned when the visitor leaves.

Laptops are allowed after a customs check to ensure they do not carry a mobile communication device.

While foreigners are left incommunicado at the terminal, North Koreans chat on their own mobiles.

The country in December 2008 introduced a 3G network in a joint venture with Cairo-based Orascom Telecom.

Chosun Sinbo, a pro-North Korean newspaper published in Tokyo, reported in April that there were only 120,000 mobile subscribers in North Korea, a country of 24 million people.

Tour guides and officials are among those with mobiles although, unusually for Pyongyang, two girls were also seen intently focused on their handsets as they sat in a park.

Anywhere else in Asia the scene would have been routine but it was a rare sight in the run-down capital which seems stuck in a time decades past.

The regime is expanding its wireless network to accommodate about 600,000 subscribers before the end of this year, the Chosun Sinbo paper said.

Mobiles used in Pyongyang are made in neighbouring China.

Tour guides said the poverty-stricken country has a "local" Internet service and they thought that an outside link to the real Internet existed, perhaps at a library or university.

The Yanggakdo International Hotel, one of two "deluxe" hotels catering to foreigners in the capital, has a telephone kiosk in the lobby.

International calls are crystal clear and a computer in the corner offers email, the clerk says.

"But no Internet," she adds.

While the world's high-tech revolution has passed the country by, visitors assume it is up-to-date in one area: surveillance.

In an elevator of the Yanggakdo, one loud foreigner was cautioned by another who expressed concern about listening devices.

"Hotel rooms, telephones, and fax machines may be monitored," the United States State Department advises travellers.

North Koreans are bombarded with propaganda from childhood, leaving them in ignorance of the wider world. One tour guide had never heard of the late pop star Michael Jackson.

The tuning controls of radios and televisions are fixed to official stations.

In Pyongyang, an evening of local television likely involves a movie about North Korea's past wars.

The BBC, Japan's NHK, CCTV from China, and a Russian channel are, however, available in rooms at the Yanggakdo.

Several rights groups in South Korea have contacts who relay news via Chinese cellphones with pre-paid cards, but these work only in border areas.

Activists say authorities operate cars with special equipment to detect unauthorised cellphone signals along the Chinese border.

In March, the Seoul-based rights organisation Free North Korea Radio said it had given three satellite phones to "correspondents" in the North to try to break down the country's wall of secrecy.