A giant sinkhole that swallowed part of a five-lane road in the Japanese city of Fukuoka has been filled in with a speed almost as astonishing as its sudden appearance.

Before-and-after photos of the road show people walking across a pedestrian crossing that, just days ago, was a gaping hole roughly half the size of an Olympic swimming pool in the southern Japanese city's central business district.

Despite the remarkable efficiency of the repair effort, the mayor of Fukuoka, Soichiro Takashima, offered an earnest apology to those who had been inconvenienced.

"We're very sorry for causing great trouble," he said in a statement.