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.

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.

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