A photo taken of Potala palace in the distance on Monday, March 24, 2008. The renovation work of Potala and Norbu Lingka palaces, two major cultural heritage sites in Lhasa, the capital of the southwestern Tibet Autonomous Region, resumed early this month. [Photo: Xinhua]

Renovation of two major cultural heritage sites in Tibet resumed earlier this month amid warming spring weather after being suspended during the freezing winter, a local official said on Tuesday.

Workers returned to the Potala and Norbu Lingka palaces in Lhasa, the capital of the southwestern Tibet Autonomous Region, Nyima Cering, who is in charge of the repair work, told Xinhua.

The recent unrest in Lhasa interrupted the movement of construction materials for a couple of days, but the situation has returned to normal and the projects are proceeding in an orderly way, said the official.

Nyima said security measures were stepped up to protect the palaces and the safety of the staff after violence broke out on March 14.

Workers were awaiting better weather to resume work on another cultural heritage site, Sagya Monastery, which is at a much higher elevation.

"We plan to restart work in April, weather conditions allowing," said Nyima.

Work on the three sites began in 2002 and was expected to be finished this year. The cost of about 330 million yuan (about 47 million U.S. dollars) would be paid by the central government.

About 77 percent of the money has been spent and 129 minor projects under the program have passed quality examinations.

The Potala Palace, built in the 7th century, is on the world cultural heritage list. Norbu Lingka, which means "treasure park" in the Tibetan language, was the summer palace of the Dalai Lama. Sagya Monastery houses numerous classical books on Buddhism and precious paintings.

Over the past two decades, the central and local governments have spent more than 700 million yuan to preserve and maintain about 1,400 historical and cultural relics in Tibet, including monasteries.