China on Thursday increased the maximum speed of bullet trains on the Beijing-Shanghai high-speed railway to 350 kilometers per hour, six years after it was reduced to 300 kmh.

A bullet train named Fuxing (meaning "rejuvenation" in Chinese), which will travel at the new high speed, departed Beijing South Railway Station at 9:00 a.m. for Shanghai.

The speed increase will cut the Beijing-Shanghai journey to 4 hours and 28 minutes.

"These trains are so popular that the tickets for today already sold out a week ago," said Huang Xin, an official with the China Railway Corporation, on Thursday.

Connecting the Chinese capital with the major financial and trade hub, the Beijing-Shanghai high-speed railway is one of the busiest in the country, carrying more than 100 million passengers a year.

China has the world's longest high-speed rail network, with 22,000 kilometers in operation so far.