HONG KONG (AFP) - The world's longest sea bridge, connecting Hong Kong, Macau and the Chinese mainland will open to traffic next Wednesday (Oct 24), officials said, after complaints about the secrecy surrounding the project.

A grand opening ceremony had already been announced for the day before in the southern mainland Chinese city of Zhuhai - possibly attended by China's President Xi Jinping.

Hong Kong lawmakers have criticised a lack of transparency over when traffic will be able to use the bridge, while local bus companies have also complained about being kept in the dark.

The 55km crossing, which includes a snaking road bridge and underwater tunnel, links Hong Kong's Lantau island to Zhuhai and the gambling enclave of Macau, across the waters of the Pearl River Estuary.

Construction of the massive infrastructure project began in 2009 and has been dogged by delays, budget overruns, corruption prosecutions and the deaths of construction workers.

Supporters of the bridge promote it as an engineering marvel, while others see it as a costly political project designed to further integrate Hong Kong into the mainland at a time when Beijing is tightening its grip on the semi-autonomous city.