Rakuten Inc. said Wednesday it has raised its stake in Tokyo Broadcasting System Inc. to 19.09 percent, only a tad short of the TV network's 20 percent threshold for triggering a process that could lead to the activation of takeover defense measures.

The Internet shopping mall operator's latest purchases fueled images of a nasty takeover battle, as they came despite repeated pleas by TBS not to buy a bigger stake while it was studying Rakuten's merger proposal.

"We have made purchases of some additional shares in accordance with market rules," Rakuten CEO Hiroshi Mikitani told a news conference in Tokyo. "Honestly, I don't understand why we are not supposed to buy shares that are traded on the market."