The nation's industrial output expanded a seasonally adjusted 2.5 percent in January from the previous month, revised upward from the initially reported 2.1 percent increase, the Ministry of Economy, Trade and Industry said Monday.

The index of production at mines and factories registered 102.5 against the base of 100 in 2000, compared with 102.1 in a preliminary report.

The upward revision was mainly attributable to firm production of ships, METI said. It is the largest growth since April 2004, when output logged a 3.5 percent rise.