Livedoor Co. has increased its stake in Nippon Broadcasting System Inc. to more than 40 percent in terms of voting rights, officials of the Internet services provider said Monday, stepping up the pressure on Fuji Television Network Inc. in a high-profile acquisition battle.

Nippon Broadcasting is the largest stakeholder in Fuji TV, and if Livedoor succeeds in taking over the radio company, it could make its weight felt in Fuji TV's management.

Livedoor officials said the company held more than 39 percent of the voting rights stake in Nippon Broadcasting as of last Friday. Livedoor had 37.85 percent on Feb. 8, as reported by the radio broadcaster in an updated statement Monday. In terms of outstanding shares, Livedoor's stake was 34.99 percent at that time.