BRUSSELS, Belgium -- Ukrainian President Volodymyr Zelensky said Thursday there is a "real" threat that Moscow will use chemical weapons in Ukraine, accusing Russia of having already used phosphorus bombs against civilians in the country.

"The threat of full-scale use by Russia of chemical weapons on the territory of Ukraine is real," Zelensky told a G7 summit in Brussels via videolink, adding that Kyiv had information that Russian troops "used phosphorus bombs against peaceful people in Ukraine".

Kyiv first accused Russia of using phosphorus shells against civilians two weeks into its invasion of Ukraine.

The Ukrainian leader called for a "total embargo" on doing business with Russia, and for Russia to be prevented from using the GPS navigation system "in times of war".

Zelensky said Russian banks should be "completely cut off from the global financial system" and frozen Russian assets "should be used towards reparations to rebuild Ukraine".

Zelensky also warned that the war in Ukraine could lead to a "global food crisis".

"The longer there is no peace on Ukrainian territory, the less Ukrainian food the global market will receive," he said.

He said the war could lead to shortages of "basic products" in "many countries of Asia, Africa and even Europe".

Ukraine is among the biggest exporters of farm-grown food, including wheat and maize.

Russian President Vladimir Putin launched his shock invasion of Ukraine one month ago.