The world has another wall, this time on the Crimea-Ukraine border, built by the Russians, in their words "to prevent the penetration of raiding groups from the Ukrainian side".

With remote cameras and regular patrols, the 60-kilometre-long barrier is also equiipped with hundreds of sensors, similar to measures employed by Russia on its northern and eastern borders.

It is another tightening of pressure on Ukraine, and France and Germany issued a joint statement on Friday condemning it, and the recent illegal interference in maritime navigation in the Sea of Azov.

Angela Merkel and Emmanuel Macron's joint statement also underlines longstanding concerns for human rights in Crimea, illegally annexed by Russia from Ukraine in 2014, especially concerning the Tatar minority.

Russia has also made some additions to the newly-completed Crimea bridge over the Kerch strait described as special navigation equipment to "secure boat traffic". The structures also have the effect of narrowing the passage.