Ukraine war: Kyiv claims counteroffensive boost, cluster bomb concerns, '50,000 Russians dead'

Ukrainian troops have "taken the initiative" in their counteroffensive into Russian-occupied territory, Ukraine's president said on Sunday. 

"All of us, we want to do it faster because every day means new losses of Ukrainians. We are advancing. We are not stuck," said Volodymyr Zelenskyy during an interview on the US's ABC news network. 

He noted Ukraine's military had overcome a "kind of stagnation" in previous months.

"We would all love to see the counteroffensive accomplished in a shorter period of time. But there is a reality. Today, the initiative is on our side."

Moscow has said there is heavy fighting around the eastern city of Bakhmut,  captured by Russian mercenary Wagner forces in May after months of gruelling warfare.  

Chechen leader Ramzan Kadyrov said one of his units was deployed in the area.

Furnished with advanced Western weapons and training, Ukraine launched its much-anticipated counteroffensive in June, aimed at capturing a cluster of villages in the southwest and retaking areas around Bakhmut.

Ukrainian forces have encountered stubborn Russian resistance. 

President Joe Biden's controversial decision to send cluster bombs to Ukraine has been criticised by two US Democrats, Senator Tim Kaine and Representative Barbara Lee.

Washington announced on Friday it would supply Kyiv with the widely banned munitions as part of a new €730 million aid package. 

The move was widely condemned by rights groups, while the US's NATO allies distanced themselves from it. 

"Cluster bombs should never be used," said Representative Lee to the CNN new channel on Sunday. "That's crossing a line." 

She added the US risked losing its "moral leadership" by sending cluster bombs to Ukraine.

Cluster bombs are prohibited by more than 100