European leaders in defiant Kyiv trip as Russia closes in

A trio of eastern European leaders met Ukraine's president in his besieged capital Tuesday, in a defiant act of solidarity as Russian forces pressed in and air strikes claimed yet more lives in the city under curfew.

As talks ground on between Moscow and Kyiv in a bid to halt the devastation, the White House upped the ante by announcing President Joe Biden will visit Europe next week to shore up NATO's unity as war rages on its eastern flank.

The nearly three-week-old conflict has revived Cold War-level tensions between Moscow and the West and sent more than three million Ukrainians fleeing across the border to seek refuge in neighbouring states.

On the ground in southern Ukraine the presidency reported a humanitarian breakthrough of sorts, with some 20,000 residents evacuating from the besieged port city of Mariupol where there is a critical lack of food, water and medicine.

Exhausted, shivering evacuees spoke of harrowing journeys out of the city of 400,000, and a stench of death on the streets.

"Sometimes bodies are in the street for three days. The smell is in the air and you don't want your children to smell it," said Dmytro, a refugee who arrived with his wife and two young children in Zaporizhzhya on Tuesday.

Despite the developments on evacuations, mixed messages emerged from the latest negotiations. 

Both Moscow and Kyiv signalled progress, but a Ukrainian presidential aide, Mykhailo Podolyiak, cautioned that while "compromise" was possible, "fundamental contradictions" remained.

Kyiv was "not showing a serious commitment to finding mutually acceptable solutions," Russian President Vladimir Putin told European Council leader Charles Michel in a call Tuesday.

Russia extended its military onslaught elsewhere, including a huge strike on an eastern airport, while four people were killed in strikes on homes in the capital.

As a 35-hour curfew came into force in Kyiv, President Volodymyr Zelensky hosted the Polish, Czech and Slovenian prime ministers in the first visit to the city by foreign leaders since Russia's invasion.