The general staff of Ukraine's armed forces and members of three brigades serving in the Donetsk region in eastern Ukraine said they had noticed a recent change compared to the start of the year.

"It's become better over the past month and it keeps getting better, at least for 155mm calibre artillery shells," a Ukrainian sergeant using the call sign "Luntik" -- a type of military nickname -- told AFP.

He said that in the first quarter of the year, ammunitions in his unit had been strictly rationed to "six shells every 24 hours" while the limit today was "up to 40 per day", the sergeant said.

In areas like the Kharkiv region, where Russia launched a land offensive last month, he said that "there is no limit".

In Kharkiv "the occupier has failed," President Volodymyr Zelensky said on Friday, while admitting the situation remained difficult.

"Our Ukrainian forces have stabilised the situation and stopped the offensive," he said.

The outnumbered Ukrainian army has been heavily reliant on Western supplies against its better armed enemy.

Ukrainian forces have been particularly vulnerable since the end of 2023 because of major delays in European and US arms deliveries.

The US Congress in April voted through a $61-billion aid package for Ukraine but deliveries to the frontline can take weeks or even months.

New supplies have still not brought levels back to those of 2023 "but it seems we should reach the same level soon", said the sergeant.

An artillery serviceman in a different brigade in the same region said: "It has become a lot better."

But another soldier in a third brigade said: "Unfortunately the enemy still has an advantage in terms of personnel and artillery systems."

"For a war of this intensity, we will need more and more," he said.

Luntik said that even when Ukrainian forces destroy Russian artillery systems, "they are replaced the next day".

According to a source at the general staff, the ratio between Ukrainian shelling and Russian shelling has moved in Kyiv's favour thanks to the arrival of new Western supplies.

"At the moment, the ratio of use of ammunition is one to three" in Russia's favour, compared to "one to seven" before.

"Our supplies have gone up and theirs have gone down," he said.