The National Museum of China, the grand building on the east side of Tian'anmen Square in downtown Beijing, closed today for a three-year overhaul that will make it the world's largest arts and history museum.

The museum's floor space will be expanded from the current 65,000 square meters to 192,000 square meters turning it into the world's most spacious, said a source with the museum.

"It does not have enough display and storage space, and some exhibition halls are becoming less safe due to old age," the source said, adding that the museum can't ensure the safe keeping of its relics as standards are below that of a top-level state museum.

"When it re-opens, its displays, security measures, and services will all be equal to a world-class museum," the source said.

The National Museum, which was formerly the Museum of the Chinese Revolution was built in 1959. It houses hundreds of thousands of cultural relics from different periods of China's 5,000-year history. It is home to millions of scrolls and other cultural relics.

The source said most of the precious relics will be stored at a special site during the renovations.

Some of relics will be displayed at the Capital Museum of China during the Beijing Olympic Games in 2008, the source said.

Construction work will start in April, the source said.