President Tayyip Erdogan on Friday opened a gigantic suspension bridge across Turkey's Dardanelles Strait, connecting the country’s European and Asian shores.

The bridge, built by Turkish and South Korean firms with an investment of $2.8 billion, has the longest main span in any suspension bridge in the world.

The 2,023 metre length of its midspan refers to Turkey’s 100th anniversary in 2023.

Its towers are 318 metres high and the total length of the bridge is 4.6 km including the approach viaducts.

Work on the Dardanelles bridge project was launched in March 2017, with more than 5,000 workers involved in the construction.

Vehicles travelling between Anatolia and the Gallipoli peninsula had to cross the Dardanelles in a one-hour ferry journey, which including waiting time amounted to as much as five hours. The journey will now take around six minutes.

"These works will continue to provide profit for the state for many years," Erdogan said at an opening ceremony on the anniversary of a 1915 Ottoman naval victory against French and British forces in the Dardanelles during World War One.

"These projects have a large share in putting our country ahead in investment, workforce and exports," he said.

Ahead of national elections scheduled for 2023, opinion polls have shown a drop in Erdogan’s popularity.

The main opposition party CHP has criticised the potential cost of the bridge to the national exchequer, with media reports saying the build-operate-transfer agreement includes an annual payment guarantee of $420 million to the operators.