Ukraine says rescue under way after naval vessel attacked from shore

A Ukrainian naval vessel in the Azov Sea was attacked by artillery from the shore on Sunday, and a rescue operation was under way, a military spokesman for the Ukrainian government said.       

Andriy Lysenko said the vessel was a naval cutter. There was no information on the number of people on board.        

Pro-Russian rebels claimed responsibility for the attack on social media.

Earlier on Sunday, Ukraine and Russia swapped soldiers who had entered each other's territory near the battlefield in eastern Ukraine, where Kiev says Moscow's forces have come to the aid of pro-Russian insurgents advancing for an assault on a major port.
 
Ukrainian troops and local residents were reinforcing the port of Mariupol on Sunday, the next big city in the path of pro-Russian fighters who pushed back government forces along the Azov Sea this past week in an offensive on a new front.
 
The new rebel advance has drawn increasing concern from Ukraine's Western allies, who say its success is a result of reinforcement by armored columns of Russian troops.
 
European Union leaders agreed on Saturday to draw up new economic sanctions against Moscow, a move hailed by the United States, which is planning tighter sanctions of its own and wants to act jointly with Europe.
 
Some residents of Mariupol have taken to the streets to show support for the Ukrainian government as the pro-Russian forces gain ground. Many others have fled from the prospect of an all-out assault on the city of nearly 500,000 people.