Kiev (AFP) - The Sea of Azov, scene of a new escalation in tensions between Ukraine and Russia, is joined to the Black Sea by a narrow strait that is a vital shipping lane for both the rival nations.
Here is some background.
- Vital Black Sea link -
Wedged between Russia, Ukraine and Crimea, the Sea of Azov is a northern extension of the Black Sea to which it is linked via the Strait of Kerch, which is just 15 kilometres (nine miles) wide.
Dotted by busy industrial ports, the sea's sole access to the Black Sea -- and so the Mediterranean further along -- is this strategic strait.
A treaty signed between Ukraine and Russia in December 2003 provided for common management of the sea and the strait. It did not, though, demarcate the maritime border between the two countries.
Russia's internationally condemned annexation from Ukraine of the Crimea peninsula in 2014 gave it control of both sides of the strait, and Moscow has been accused of since squeezing access for Ukrainian ships.
The Sea of Azov is the shallowest sea in the world, with a maximum depth of just 14 metres (46 feet). It is also small at around 360 kilometres long and 180 kilometres wide.
- New bridge enflames tensions -
A Russia-built bridge over the Strait of Kerch and linking mainland Russia to Crimea was inaugurated in May 2018, infuriating Ukraine and its EU and NATO allies.
President Vladimir Putin personally championed the Crimean Bridge project, important in reducing Crimea's reliance on sea transport for supplies, saying it was the realisation of Russia's historic ambitions.
But Ukraine says its larger ships are unable to get under the bridge's 35-metre arches to and from its ports on the Azov Sea.
The result for Ukraine is a significant drop in shipping traffic and economic losses.
Condemning the opening of the 19-kilometre bridge in May, the EU said it entrenched the "forced integration" of Crimea with Russia, and "its isolation from Ukraine."
In July the EU expanded its sanctions against Moscow to include companies involved in the bridge's construction.
- Key Ukraine port -
Ukraine's important port city of Mariupol is situated on the northern edge of the Sea of Azov and has vital access to heavy industry in the eastern part of the country.
It is the only major city in southeastern Ukraine under government control since pro-Russia separatists seized parts of the east in the wake of the annexation of Crimea.
This includes the Russian-backed rebel Donetsk and Lugansk regions, whose conflict with Kiev has caused at least 10,000 deaths since 2014.
Mariupol, home to around 500,000 people, is dominated by two vast iron and steel businesses which together employ tens of thousands of people.
Kiev and the West have accused Moscow of deliberately blocking ships from accessing the commercial port, some 55 kilometres (35 miles) from the Russian border.
Ukrainian media have reported that the Mariupol and the Berdyansk port saw earnings fall by almost a quarter during the first seven months of this year, compared with the same period last year.