New Delhi, The war in Ukraine will deliver a shock to the global supply and cost of food, the boss of one of the world's biggest fertiliser companies has said, BBC reported.

Yara International, which operates in more than 60 countries, buys considerable amounts of essential raw materials from Russia.

Fertiliser prices were already high due to soaring wholesale gas prices.

Yara's boss, Svein Tore Holsether, has warned the situation could get even tougher.

"Things are changing by the hour," he told the BBC.

The Yara International chief executive describes the war as "a catastrophe on top of a catastrophe", highlighting just how vulnerable to shocks the global food supply chain now is.

It will increase food insecurity in poorer countries, he adds.

"We have to keep in mind that in the last two years, there's been an increase of 100 million more people that go to bed hungry... so for this to come on top of it is really worrying."

"Half the world's population gets food as a result of fertilisers... and if that's removed from the field for some crops, (the yield) will drop by 50 per cent," Holsether said.

"For me, it's not whether we are moving into a global food crisis - it's how large the crisis will be"

"We were already in a difficult situation before the war... and now it's an additional disruption to the supply chains and we're getting close to the most important part of this season for the Northern hemisphere, where a lot of fertiliser needs to move on and that will quite likely be impacted."

Russia and Ukraine are some of the biggest producers in agriculture and food globally.

Russia also produces enormous amounts of nutrients, like potash and phosphate -- key ingredients in fertilisers, which enable plants and crops to grow, BBC reported.