Non-regular workers in Japan have gone on strike demanding higher wages.

Last year, part-time workers and temporary staff including those whose workplaces have no labor unions began seeking wage hikes from their employers.

This year, more than 20 unions and other groups open to freelancers have been negotiating with 120 employers for across-the-board wage hikes of 10 percent or more.

Some employers have agreed to a raise, but many have not responded fully to workers' demands.

About 500 non-regular workers at 15 companies plan to stage strikes from Wednesday through the end of this month.

On Wednesday, about 50 people gathered outside one of the companies. They claimed that life for non-regular workers is becoming harder, and they deserve a raise.

There were some 21 million non-regular workers in Japan last year, making up 37 percent of the country's work force.

Unions at major companies have secured high-level pay deals with management. It is uncertain whether non-regular workers can benefit from this trend.

A man in his 50s who works as a part-time teacher at a cram school said at a news conference that he is worried because prices are going up but his wage is not keeping pace.

He said he will fight on because his wage will drop further if he is rehired after official retirement age.

Co-leader Aoki Kotaro of General Support Union, which called on non-regular workers to take part in wage negotiations, says that while workers at big companies have quickly had their wage hike demands fully accepted, this is not the case for non-regular workers.

He says it is important to have a framework where even one person can seek a wage hike, as many non-regular workers have no unions to join.