Japanese Prime Minister Shinzo Abe's ruling coalition was on track to expand its majority in upper house elections on Sunday, according to public broadcaster NHK.

Abe's Liberal Democratic Party and its coalition partner Komeito would take between 67 to 76 of the 121 seats -- half the chamber -- available in the election, up from 59 previously, NHK said.

NHK's projection, based on exit polling and other analysis, came immediately after polls closed at 8 pm (1100 GMT).