The G7 group of industrialised nations are united in backing Ukraine "until victory", France said Friday, as the EU promised more military aid for Kyiv in its fight against Russia's invasion.

"It is very important at this time that we keep up the pressure on Vladimir Putin by supplying more weapons to Ukraine, by increasing the sanctions," said British Foreign Secretary Liz Truss as she arrived for a second day of talks with her G7 counterparts in northern Germany.

"G7 unity has been vital during this crisis," she added.

French Foreign Minister Jean-Yves Le Drian said the G7 countries were "very strongly united" in their will to "continue in the long term to support Ukraine's fight for its sovereignty until Ukraine's victory".

Underlining their resolve, EU foreign policy chief Josep Borrell said the bloc was pledging an extra 500 million euros ($520 million) in military aid.

The cash will raise the EU's total military aid for Ukraine to two billion euros, he said.

"The recipe is clear –- more of the same," Borrell said. 

"More pressure on Russia, with economic sanctions. Continue working on international isolation of Russia. Countering the disinformation about the consequences of the war... And presenting a united front to continue supporting Ukraine."

The foreign ministers are meeting over three days in the resort of Wangels in Germany, which currently holds the presidency of the G7.

The war in Ukraine is set to be the main topic on the agenda, with Ukrainian and Moldovan foreign ministers Dmytro Kuleba and Nicu Popescu also on the guest list.

Repugnant

Separately in the south-western German city of Stuttgart, agriculture ministers of the G7 as well as their Ukrainian counterpart have gathered to discuss how to head off a looming international food crisis sparked by the war.

Accusing Russia of theft from Ukrainian farmers, Germany's agriculture minister said this was "an especially repugnant form of war that Russia is leading, in that it is stealing, robbing, taking for itself grain from eastern Ukraine."

Russia invaded Ukraine on February 24 but Ukrainian forces managed to push Moscow's forces back from Kyiv, and the conflict is now well into its third month.

Western countries have supplied Ukraine with weapons, including artillery, anti-aircraft missiles, anti-tank weapons and other powerful materiel, but Kyiv has been pushing allies for more support.

Le Drian also pointed to the global effects of what he called a "lasting conflict... particularly in the area of food security".

German Foreign Minister Annalena Baerbock had also on Thursday highlighted the growing impact of the war on poorer countries.

"We as the strongest industrialised democracies have a special responsibility" to help poorer nations weather the food and energy squeezes caused by the war, the said.