North Korea and Russia have begun building their first road link, the two countries announced, hailing the construction of a bridge over a border river as a major development that will further expand their booming ties.

The announcement comes after North Korea confirmed for the first time its soldiers are fighting alongside Russia.

North Korea said the construction of a new bridge linking it to Russia is a "significant" development of relations between the two countries, state media KCNA reported on Thursday. Russia and North Korea on Wednesday began construction of a road bridge that will span the Tumen River.