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.