Ukraine crisis: Border patrol boat sunk in first naval attack as Ukrainian conflict continues to escalate

President Poroshenko claims Russia has launched 'a direct and open aggression' against Ukraine

A Russian fighter atop a tank, photographed yesterday southeast of Donetsk (AFP)

Two Ukrainian seamen are missing after a pro-Russian attack on a patrol boat in the Sea of Azov yesterday as the situation in the region continues to escalate.

This morning Ukrainian President Petro Poroshenko accused Russia of launching "direct and open aggression" which he said had radically changed the balance on the battlefield against Kiev in its fight against pro-Russian separatists.

Eight further men were rescued when the border guard vessel capsized after it was allegedly fired on by land-based separatist forces, in the first naval action of the conflict.

A Ukrainian official, Serhiy Astakhov, said: "After analysing the situation, we believe that this attack was from an artillery system but we don't know yet where it was fired from”.

The attack will stress fears the rebels are trying to seize a land bridge between Russia and the Crimean Peninsula, which Russia annexed in March.

Just hours after the latest escalation president Putin called for talks on eastern Ukrainian ‘statehood’, stoking fears of a Russian claim to the territory – despite his spokesperson then claiming his remarks should not be taken as an endorsement of rebel calls for independence.

In a speech at a military academy in Kiev, president Poroshenko said: "Direct and open aggression has been launched against Ukraine from a neighbouring state. This has changed the situation in the zone of conflict in a radical way".

Yesterday Ukraine exchanged 10 Russian soldiers, seized inside the country last week, for 63 Ukrainian servicemen.

The situation in Ukraine continues to deteriorate, with Western leaders largely standing by.

Over the weekend European leaders warned the presence of Russian troops in Ukraine posed a serious threat to the whole continent, as some called for a dramatic escalation of the EU’s response to Russia which so far has largely consisted of economic sanctions.

Additional reporting from Reuters