Turkey plans to build two new cities near Istanbul and relocate up to 1.5 million residents who are most at risk from a possible earthquake in the metropolis, the prime minister said on Wednesday.

"Do not forget that Istanbul is under a major threat of an earthquake ... This project would strengthen Istanbul's preparedness," Recep Tayyip Erdogan said in his televised remarks.

"Around 1.5 million people will be moved to those cities. We want our people to contribute this project from their hearts, we want them to move voluntarily," he added.

The locations for the two satellite cities had been chosen after safety studies, Erdogan said, adding that one of them would be built on the shores of the Black Sea on the European side of the city.

The second one would be on the Asian side of the Bosphorus Strait, Erdogan said, without giving any details.

The construction of the two cities would begin after June's parliamentary election, the premier added.

Erdogan announced last month plans to build a water channel connecting the Black and Marmara seas as an alternative to the congested Bosphorus Strait. A third bridge would also be constructed over the Bosphorus, in northern Istanbul.

The announcements come as part of a series of election pledges by the prime minister ahead of elections on June 12 in which his Islamist-rooted party is seeking a third straight term in power.

Istanbul's 13 million inhabitants live in constant fear of a major earthquake, which experts predict will hit Turkey's largest metropolis in the near future with a magnitude of up to 7.2.

In 1999 an earthquake, which measured 7.6 on the Richter scale, devastated Turkey's most industrialised Marmara region, including some suburbs of Istanbul, and killed some 20,000 people.