Ukraine has markedly stepped up its long-range attacks on Russian military industries and energy facilities in recent months, aiming to cut Russia's revenue for its invasion - now in its fifth year - and make the Russian population feel the consequences.
"Our 'long-range sanctions' reached two oil refineries in Russia," Ukrainian President Volodymyr Zelenskiy wrote on social media.
"Each (strike) means a reduction in the resources that fuel the Russian war machine, and another step toward peace."
Debris from downed Ukrainian drones sparked a blaze at the refinery in Slavyansk-na-Kubani, a town in Russia's Krasnodar region, east of occupied Crimea, according to Governor Veniamin Kondratyev.
The falling debris killed one person in Slavyansk and wounded another in a nearby village, local authorities said.
The Slavyansk site is one of southern Russia's major refineries, processing close to four million tonnes of crude per year, according to its operator's website.
It is also a key source of petroleum products intended for export through Russia's Black Sea ports, including fuel oil, naphtha and marine fuel.
Zelenskiy also said a second Russian refinery, in the Yaroslavl region about 700km from the Ukrainian border, was hit during the night-time strikes.
Putin acknowledged on Sunday that the country was "going through a difficult period" but insisted that the government would "honour all its social obligations" to citizens.
He did not directly reference the Ukrainian strikes or fuel shortages.
"Naturally, we are adjusting certain plans in light of the current situation but all strategically important (domestic) development programs will undoubtedly be implemented in full," Putin said at a conference of his ruling United Russia party ahead of parliamentary elections due in September.
"We will continue to build housing and roads, create new, modern, high-paying jobs, and support domestic businesses," he said.
"We are going through a difficult period but this has taught us a great deal, and allowed us to grasp the very essence of what it means to be a Russian citizen."
The constant Ukrainian attacks on oil facilities have left deeper traces in Russians' everyday lives.
The fuel crisis, which began in Crimea, which Russia annexed in 2014, has now spread to almost all regions of the country.
Long queues are forming at the service stations that are still selling petrol.
In Crimea, service stations are no longer supplying fuel to private individuals.
Meanwhile, Russian attacks killed at least four people on Sunday in Ukraine's southeast and northeast, regional officials said.
Strikes on the southeastern city of Zaporizhzhia killed two people and injured 16, Regional Governor Ivan Fedorov said on Telegram. Pictures posted online by the governor showed a building ablaze and parts of a neighbourhood reduced to rubble.
In the northeastern border region of Kharkiv, a frequent Russian target, a missile strike on the town of Zmiiv killed one person and injured eight, including two children, Regional Governor Oleh Syniehubov said.
Police in the Kharkiv region also said an officer was killed as he was trying to organise the evacuation of residents in another community further north. In the Sumy region, also on the Russian border, the regional governor said an elderly woman was killed during the day in an area near the border.
with AP and DPA
