DAVOS, SWITZERLAND (AFP) - WTO chief Ngozi Okonjo-Iweala on Wednesday (May 25) urged countries not to block or restrict exports of basic foodstuffs after Russia's invasion of Ukraine worsened tensions on global food markets.

"We're trying to tell members also on the export prohibition, restriction side, let's keep it down," Okonjo-Iweala told reporters at the World Economic Forum in Davos, Switzerland.

"We don't want this to exacerbate and lead to price spikes."

Her comments followed India's decision the same day to cap sugar exports at 10 million tonnes in the year to September, following up on a ban on wheat sales abroad.

New Delhi said the decision aimed to "maintain the domestic availability and price stability during the sugar season".

Moscow's invasion has disrupted supplies of fertiliser, wheat and other commodities from both Russia and Ukraine.

In response, "we have about 22 countries now with 41 export restrictions or prohibitions on food," Okonjo-Iweala said.

As well as foodstuffs themselves, "let's not forget inputs, seeds and fertiliser," she added.

She highlighted that the WTO hoped its public monitoring of such controls would deter member countries.

"Transparency helps," Okonjo-Iweala said.

"It helps to put pressure on members or countries that are doing this.

"For security reasons, you can do this for periods of time but it has to be temporary, transparent and proportionate, so they know it cannot go on for ever."

She also said that United Nations Secretary-General Antonio Guterres "is involved" in talks to open corridors through the Black Sea for Ukrainian food exports to reach world markets.

"I know that some work is going on behind (the scenes) to try and see if we can get a solution on that," Okonjo-Iweala added.

"There's going to be huge pressure to make (corridors) happen," McKinsey analyst Clarisse Magnin-Mallez told AFP.

There is "no option apart from transporting by sea" because of the "massive volumes" that must be shifted, she added.

Ukrainian Foreign Minister Dmytro Kuleba had earlier on Wednesday said that a Russian proposal to lift the sanctions against Moscow so as to avoid a global food crisis was "blackmail".