Ukraine war live updates: Russian forces cement hold on Avdiivka; Ukraine investigates alleged shooting of POWs in captured city

This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

Russian forces are consolidating their hold on Avdiivka after capturing the city at the weekend. Russian troops say they have now taken full control of the Donetsk city's chemical and coke plant.

Russian news agency Tass, citing Russia's Defense Ministry, stated that Russian forces had now "completely liberated the coke plant in Avdiivka, the flags of the Russian Federation have been hoisted on the buildings of the enterprise."

Russia's Defense Ministry said Sunday that some Ukrainian units were still entrenched at the plant, which used to be one of the largest of its kind in Europe.

Ukrainian authorities said on Sunday that they've launched an investigation into the alleged shooting of unarmed Ukrainian prisoners of war in Avdiivka and the village of Vesele.

The Prosecutor Office of the Donetsk region said on Telegram Sunday that a "pre-trial investigation was launched into the facts of violation of the laws and customs of war, combined with intentional murder." Russia has not commented on the allegations.

Russian investigators have not yet established the cause of Alexei Navalny's death and it is unclear how long it will take for official conclusions to be made, his mother was told, Navalny's spokeswoman said on Monday.

Navalny, a 47-year-old former lawyer, fell unconscious and died on Friday after a walk at the "Polar Wolf" penal colony in Kharp, about 1,900 km (1,200 miles) northeast of Moscow, where he was serving a three-decade sentence, the prison service said.

Navalny's mother, Lyudmila, was told on Saturday at the prison colony that he had perished from "sudden death syndrome", a vague term for different