The Alibaba-led series E round has proven the latest milestone for China's rapidly growing bike sharing sector as its biggest players look to move into foreign streets.

The $700m series E round closed by China-based on-demand bicycle rental service Ofo last week – its third nine-figure round in nine months – once again indicates the pace at which the sector is growing, and raises some tantalising questions about where it is headed.

Ofo has built a bicycle rental service that enables users to pay and unlock the bikes through a mobile app. It claims to have registered more than 100 million users across 150 cities and…