Financial regulators are expected to complete an outline by year's end amending equity acquisition rules to remove several loopholes in the securities trading system, according to sources.

The move by the Financial Services Agency follows the Murakami Fund's sudden emergence as a major shareholder in Tokyo Broadcasting System Inc. earlier this month, the sources said Tuesday.

Under existing share acquisition rules, an investor who has purchased an equity stake of more than 5 percent in a listed company is required to report information on the purchase, such as the number of acquired shares, to the Finance Ministry within five trading days of the purchase.