By Nikolai Gorshkov
TV pictures from the scene of Russia's border dispute with Ukraine near the Black Sea look like reports from a war zone.
Ukrainian border guards have been putting up defences
Ukrainian troops in riot gear have been training against the backdrop of anti-tank defences and barbed wire.
Gunboats and helicopters are patrolling the area.
Emotions are running high, their first casualty being a Russian tug-boat that was rammed and seized by Ukrainian coastguards after it had strayed across the dividing line.
The dispute has led Ukrainian President Leonid Kuchma to cut short a state visit to Latin America.
Ukraine accuses Russia of trampling on its sovereignty by building a causeway extremely close to Ukraine's territorial waters.
Moscow and Kiev have been exchanging angry remarks about the ownership of a waterway in the Kerch Straits, separating Ukraine and Russia on the northern end of the Black Sea.
Ukrainian officials say they will do whatever it takes to stop violation of the border.
Russia says it has no interest in Ukrainian territory, and is only trying to restore a natural barrier that had been protecting its shores from erosion.
Tuzla island is at the centre of the dispute
Russian Foreign Minister Igor Ivanov has appealed for calm to allow diplomats to resolve the issue.
Ukraine and Russia are still working on a treaty to deliniate their maritime border, 12 years after separation.
The straits, which link the Black Sea and the Azov Sea, are rich in fish, oil and gas reserves, and are a lucrative transit route.
Russia would like this area to be treated as internal waters of both countries, to avoid transit fees and fishing quotas.
For Ukraine these have been a valuable source of income.
Observers believe, by building the causeway, Russia is putting extra pressure on Ukraine to agree to shared ownership of the straits.
But a bigger prize may now be at stake - a common economic area, negotiated by the leaders of Russia, Ukraine, Belarus and Kazakhstan.
Members of the Ukrainian parliament have already threatened to block the move.