ZAGREB, Croatia– Ukraine on Wednesday called for greater global support to help  demine large swathes of the war-torn country, as more than 30 countries promised nearly 500 million euros ($531 million).

The pledges were made at a donors' conference on demining held in the Croatian capital Zagreb, where Ukraine's Prime Minister Denys Shmyhal told participants from 34 countries that up to a third of his Ukranian territory was contaminated with ordnance.

"The total of these pledges amount to almost half billion euros and additional contributions have been and will be made in equipment, materials and experts," Croatia's deputy prime minister Davor Bozinovic told media.

The pledges came as Ukrainian President Volodymyr Zelensky visited NATO headquarters in Brussels, where he urged allies to step up weapons supplies -- including air defence, long-range missiles and ammunition.

Ukrainian forces are locked in a bitter counteroffensive against entrenched Russian positions along a heavily-mined front line.

Mines have proven to be a formidable obstacle in slowing Ukrainian and Russian advances across the battlefield.

Both sides have relied heavily on mines to fortify their positions.

Even as the war rages on, Kyiv has called on international partners with experience in demining to help clear the ordnance.

"Russian mines and shells in Ukraine are a problem that must be solved together," Shymgal had said via video link at the start of the conference.

He said up to six million people were actively at risk from extensive mining across Ukraine that has accelerated since Russia's full-scale invasion in February 2022.

If the demining efforts are not increased "it will take many decades to clear Ukraine of mines", Shymgal noted.