Work crews rushed Wednesday to fill in a giant sinkhole that appeared in the middle of a Japanese city's bustling business district, swallowing part of a five-lane street.

Workers dumped huge amounts of wet cement and sand into the gaping hole, measuring around 30 metres (98 feet) wide and 15 metres deep, that had exposed support columns of nearby buildings at a traffic intersection in the southern city of Fukuoka.

Images of the massive sinkhole, apparently triggered by subway construction in the area, prompted fears about more collapses.

About one-third of the huge hole had been filled in by Wednesday afternoon.

"The hole stopped expanding and stabilised by yesterday afternoon. About 35 percent of the 7,000 cubic-metre hole (247,200 cubic foot) will be filled this afternoon," a city official said.

"Crews are working around the clock."

The road was expected to be fixed by Monday.

Earlier TV footage showed two separate holes steadily expanding and merging into one as they sucked in traffic lights, asphalt and soil in front of the city's main railway station, some time after 5:00 am Tuesday (20:00 GMT Monday).

Fukuoka is the biggest city on the southernmost main island of Kyushu.