Kiev (AFP) - Ukraine on Tuesday carried out tests of the top of the range Javelin anti-tank missile it recently bought from the United States to boost its arsenal against Russian-backed rebels.

Ukrainian President Petro Poroshenko posted video on Twitter showing a missile being fired and blowing up a target at a military testing ground.

"Finally the day has come," Poroshenko said after the test, which he claimed boosted Ukraine's military capabilities as it fights a long-running conflict with Russian-backed separatists in its east.

"I'm sure that as of today the military capabilities of the Ukrainian armed forces... grew significantly."

The Javelin missiles will only be used in defence when Ukrainian positions are attacked, he said.

The US in March formally approved the sale of 210 missiles and 37 launchers by contractors Raytheon and Lockheed Martin to Ukraine at a price of around $47 million.

Poroshenko on Tuesday thanked US President Donald Trump, hailing the missile deal as a "symbol of cooperation with our American partners."

The United States and its Western allies back Ukraine in its struggle to reunite its country since 2014 when Russia annexed the Crimea peninsula and Russia-backed rebels seized two eastern industrial regions.

Washington had been cautious in the past about escalating the conflict by providing advanced "lethal" weaponry to Kiev due to the risk of heightening tensions with Moscow.

But in December the US announced it would provide Ukraine with "enhanced defensive capabilities" as the war in the east drags on, having claimed more than 10,000 lives since 2014.

In recent days, there has been increased fighting in eastern Ukraine, with at least four people killed on both sides and nine wounded on Monday.

On Tuesday, rebel authorities in the Donetsk region said that an explosive device went off in a passenger bus, killing one and wounding two.