LONDON - Russia's grain harvest is set to grow by about 5 million tonnes a year thanks to its incorporation of four Ukrainian territories, Agriculture Minister Dmitry Patrushev said on Tuesday.

"Considering the arable land that exists there, I think at least 5 million tonnes of grain will be added to the Russian savings box. I also think that we'll get other crops," he was quoted as saying by the state news agency TASS.

The Kremlin said that President Vladimir Putin was likely to sign laws on Tuesday to annex the Donetsk, Luhansk, Kherson and Zaporizhzhia regions, representing about 18% of Ukraine's internationally recognised territory.

All are partly or mostly occupied by Russian forces after an invasion that has sharply reduced Ukraine's grain crop and disrupted shipping in the Black Sea, as well as triggering a barrage of Western economic sanctions against Russia.

The resulting disruptions to grain and fertiliser flows have prompted the worst food security crisis in at least 14 years, with some 345 million people facing life-threatening shortages, the International Monetary Fund said last Friday.

Ukraine has accused Russia of stealing grain from the territories it has seized. Russia denies this.

Russia declared the annexations after holding what it called referendums in the occupied areas of Ukraine. Western governments and Kyiv said the votes breached international law and were coercive and non-representative.

Moscow's Agriculture Ministry said in August that Russia might not reach its expected harvest of 130 million tonnes of grain this year due to weather factors and a lack of spare parts for foreign equipment, and might have to revise its plans to export 50 million tonnes.

(Writing by Kevin Liffey; Editing by Robert Birsel)