Authorities in Shanghai and Tianjin will impose regulations on the rapidly growing bike-sharing sector following mounting complaints over an accumulation of millions of the rentable two-wheelers on city streets, state media reported.

The two metropolises have drafted rules that will require operators "to adhere to standards on production, operation and maintenance" of bicycles, Xinhua news agency said in a report late Wednesday.

The regulations, to take effect October 1, will mandate a service life of three years for bikes and require companies to hire at least one maintenance employee for every 200 bicycles, it said.

It added that there were now more than 10 million such bikes on the streets of Chinese cities, operated by more than 30 companies.

China's bike-sharing sector has exploded from virtually nothing about a year ago into a transport phenomenon in major cities.

Market entrants have flooded streets with the GPS-enabled bikes that users can unlock via a smartphone app, use as long as they want, and then leave anywhere.

China's government has thrown its support behind the concept as a cheap, convenient, and green transport option, and leaders Ofo and Mobike have attracted hundreds of millions of dollars in venture capital.

Much of this has been poured into putting more bikes on streets in a race for market share.

But concerns have mounted over haphazardly parked bikes cluttering sidewalks, too many operators piling in with little business planning, and customer payment disputes.

Earlier this week, China's central government issued broad guidelines for the sector designed to encourage "prudent" growth of the sector and "orderly" competition.

There were nearly 19 million users of shared bikes as of the end of 2016, Xinhua said, citing China's E-commerce Research Center.

But it quoted a Shanghai consumer affairs official saying there were more than 2,600 complaints about shared bikes in the city in the first four months of this year, nine times more than the same period in 2016.

The report also quoted officials saying Shanghai had more than a million such shared bikes in operation, twice what the city needs, but far too few maintenance personnel to deal with broken-down bicycles.