Japanese Prime Minister Shinzo Abe's ruling coalition is set to win a decisive victory in an election in the upper house of parliament.

The win will give the coalition control of both houses and a mandate to press ahead with difficult economic reforms.

Public broadcaster NHK said that Mr Abe's Liberal Democratic Party (LDP) and its partner, the New Komeito party, had won at least 74 of the 121 seats up for grabs in the 242-seat upper house.

With the coalition's uncontested 59 seats, that ensures it a comfortable majority, tightening Mr Abe's grip on power.

Controlling both houses of parliament has been an elusive goal for governments in recent years.

It has been hard to pass legislation with a divided parliament.

Mr Abe lost upper house elections in 2007 when he was prime minister then, but returned to power after his coalition's big win in a December lower house poll.

Today, he said that he would focus on fixing the world's third-biggest economy.

He plans to use a mix of hyper-easy monetary policy, fiscal spending and a growth strategy including reforms such as deregulation.

"We've argued that our economic policies aren't mistaken, and the public gave us their support. People now want to feel the benefits. The economy indeed is improving," Mr Abe said at LDP headquarters after his ruling coalition's victory was assured.

"We'd like to do our best to generate a positive cycle - in which job conditions improve and wages rise, boosting personal consumption and prompting companies to invest more - as soon as possible," he added.

But some, including Japanese businesses with a big stake in the matter, worry Mr Abe will shift to focus on the conservative agenda that has long been central to his ideology.

That agenda includes revising the post-war pacifist constitution, strengthening Japan's defence posture and recasting Tokyo's wartime history with a less apologetic tone.