In this handout screengrab taken from footage of the State Emergency Service of Ukraine released on March 13, 2022, firemen work on the aftermath of airstrikes on residential buildings in Chernihiv early on March 13, 2022. AFP
International law prohibits the use of white phosphorus shells in heavily populated civilian areas but allows them in open spaces to be used as cover for troops.
Oleksi Biloshytsky, head of police in Popasna, around 100 kilometers (60 miles) west of Lugansk city, said late Saturday that Russian forces had used the chemical weapon in his area.
"It's what the Nazis called a 'flaming onion' and that's what the Russcists (an amalgamation of 'Russians' and 'fascists') are dropping on our towns. Indescribable suffering and fires," he wrote on Facebook.
It was not immediately possible to verify the comments.
The Lugansk and Donetsk regions of eastern Ukraine, collectively known as the Donbas, were partially controlled by Moscow-backed separatist rebels before the full-scale Russian invasion of Ukraine on February 24.
Overnight on Saturday, a train evacuating people from the Donbas to the western city of Lviv was shelled, according to Donetsk military commander Pavlo Kirilenko.
One person was killed and another wounded, he said.
Two Orthodox churches sheltering civilians in the Donbas were also hit, the regional authorities said -- the renowned Sviatoguirsk church in the Donetsk region and a church in Severodonetsk, Lugansk.
There were no details of any casualties.
The areas targeted were not within the so-called separatist "republics" of Lugansk and Donetsk declared by the pro-Russian rebels before the start of the war.