“It’s hard for Russians to use the S-300 missiles right now. That was the main weapon for them to attack the Kharkiv direction and now it’s harder for them to use it,” Mr Syniehubov told The Telegraph.
“This will let the Ukraine army be more effective and the allies’ weapons will also help us to ruin their logistics.”
Moscow’s renewed assault on the Kharkiv region of north-east Ukraine was accompanied by a sharp increase in air and missile attacks.
Kharkiv, a city of 1.4 million about 19 miles from the border, was hit 76 times in May, with glide bombs, missiles and drones, the mayor, Ihor Terekhov, reported earlier this week. That was three times as many strikes as in April.
Mr Terekhov said there were now early indications the situation appeared to be improving.
“We are already feeling that the situation is different,” he said.
“Now it is too early to speak about details, but what we are seeing is their systems, the S-300 and S-400, were completely destroyed.
“These systems were used to target residential buildings and official buildings and they were using that a lot.”
Throughout the conflict, Russian forces have used surface-to-air missiles such as the S-300 and its more advanced cousin against Ukrainian cities.
While the strikes with Western weapons had improved the situation, city officials said Kharkiv still needed extra air defence systems for protection.
Ukraine is also urging its allies to further loosen the restrictions governing the use of their weapons against Russia.
Washington has agreed that Kyiv can use US weapons for “counter-fire purposes in Kharkiv so Ukraine can hit back at Russian forces hitting them or preparing to hit them”.
Washington’s new stance is thought to allow for US-supplied weapons to be used to strike Russian forces that are attacking or preparing to attack.
But Ukraine is still not allowed to use American-provided ATACMS or long-range missiles and other munitions to strike inside Russia, US officials have said.
Meanwhile, the eastern front lines have moved very little in recent weeks after a string of Russian victories in the spring put key tactical cities like Chasiv Yar under threat.