NHK has learned that the offices of more than 10 lawmakers of Japan's main ruling Liberal Democratic Party are each thought to have received kickbacks of over 10 million yen, or about 69,000 dollars, from selling tickets for political fundraising events.

Sources say the payments were made during the five years through last year. They say the political organizations of those lawmakers are suspected of having failed to declare the revenues as income in their political funds reports.

The sources say the lawmakers include Chief Cabinet Secretary Matsuno Hirokazu, LDP Diet affairs chief Takagi Tsuyoshi and the party's Upper House secretary general Seko Hiroshige.

The more than 10 lawmakers belong to the largest LDP faction, the Seiwa policy study group. The group allegedly paid kickbacks to its member lawmakers who exceeded their ticket sale quotas.

The group is accused of failing to declare the extra income and the payouts to lawmakers as expenditures in its political fund reports. The faction was once led by late Prime Minister Abe Shinzo.

Dozens of lawmakers belonging to the faction are believed to have received kickbacks from selling party tickets.

Tokyo prosecutors are believed to be considering questioning lawmakers on a voluntary basis in a bid to unravel the flow of funds.