SEOUL – Russia and North Korea have reopened a rail link that Pyongyang hopes will offer a trading boost to the isolated, sanctions-squeezed state.

The 54-kilometre (33-mile) track from the Russian border town of Khasan to the North Korean port of Rajin was opened for service at a special ceremony on Sunday, the North's official KCNA news agency reported.

Rajin is the centrepiece of the Rason Special Economic Zone established by North Korea in 1991 in an apparent effort to emulate the success of similar zones set up by China.

Located in the far northeast where the borders of North Korea, Russia and China converge, Rajin was chosen because of its potential as a warm-water port for the North's two giant neighbours.

At a summit in 2001, North Korea's late leader Kim Jong-Il and Russian President Vladimir Putin agreed to restore the rail link, as part of a joint project that included a container terminal in Rajin.

Work on the railway line began in 2008.

Since receiving special economic zone status more than two decades ago, Rason has largely failed to fulfil expectations, but development activity there has gained momentum in the last few years.

Rajin's potential as a lucrative trading hub is an increasingly attractive prospect for a country burdened by a raft of international sanctions imposed over its nuclear weapons programme.

Initially, the rail link will transport Russian coal supplies to Asia-Pacific markets.

The initial vision was for the Khasan-Rajin link to eventually become part of the so-called "Iron Silk Road" – a rail network spanning Asia and Europe.

But that idea envisages a train service linking the entire Korean peninsula – a project that looks like being held permanent hostage to volatile North-South Korean relations.