The Wall Street Journal reported that Poland has sent a dozen Soviet-designed Mi-24 helicopters to Ukraine. 

The report notes however that Ukraine's fleet remains relatively ineffective in comparison to Russia's advanced air systems. 

The aircraft delivery has not been previously disclosed, the newspaper reported.

Read more: Mike Pence: US will surely go to war with Russia if Ukraine falls

Earlier this week, at a press conference during his visit to Slovakia, Ukrainian President Volodymyr Zelensky called on the NATO alliance to resolve its indecision regarding Sweden and Ukraine's membership. 

Zelensky, who has been increasingly frustrated with the cautiousness of his Western allies in meeting Ukraine's demands, warned that indecision presents the alliance as being weak. The Ukranian chief added that expanding the alliance by admitting Ukraine and Sweden "is very important for the security of the whole world."

He also said he expects to receive "defense packages" at the summit. "And not just promises, but with clear deadlines." 

In the same context, it was also reported today that President Erdogan seemed to leave leeway for Sweden's NATO accession as he was quoted saying by AFP that Turkey would "make the best decision, whatever it is" at next week's alliance summit in Vilnius. 

"On Tuesday in the leadership summit to be held in Vilnius, we will be discussing (Turkey's concerns) with our partners. We will make the best decision, whatever it is," he said in televised remarks.

Read more: NATO to agree on Ukraine accession, but only 1-2 years after war: MoD