According to the independent Russian news agency Astra, an explosion has rocked a gas plant in the Russian city of Grozny, capital of the semi-autonomous republic of Chechnya.

Footage posted on social media shows the gas station being hit by a massive explosion, creating a large fireball and sending debris into surrounding areas. Newsweek has not independently verified the authenticity of this footage.

Chechnya is largely ruled by Ramzan Kadyrov, a pro-Russian strongman installed by the Kremlin after two devastating wars between Chechen separatists and Islamic fundamentalists in the 1990s and 2000s. In recent months, Russian infrastructure and military facilities have been repeatedly hit by Ukrainian drones, but the cause of Saturday’s explosion is unclear.

Ukrainian media outlet RBC-Ukraine said the gas station that exploded was near a university. Citing pro-Kremlin Telegram channels, it said at least four people were injured, including a mother and a child who were hit by debris from the explosion. No official death toll has been released and it is unclear what caused the explosion.

Newsweek contacted the Russian Foreign Ministry via email outside regular office hours on Saturday seeking comment.

Tensions have been rising in Russia’s restive Caucasus region, which includes Muslim-dominated Chechnya. Kadyrov this week threatened to declare a “blood feud” against Russian lawmakers from the neighboring regions of Dagestan and Ingushetia who he said were involved in a murder plot against him.

Kadyrov said the blood feud would begin unless State Duma deputies Bekkhan Barakhoev and Rizvan Kurbanov and Dagestan senator Suleiman Kerimov could prove they were not involved in the alleged plot.

In September, two security guards were shot dead at the Moscow branch of Wildberries, Russia’s largest online retailer. This was reportedly a business dispute between men loyal to Kadyrov and Russian politicians whom he threatened with a blood feud. Kadyrov called the claim that he was involved in the incident an attempt to “pit entire nations against each other over domestic disputes.”

Three people were killed on Friday in Ingushetia, a neighboring country of Chechnya, after a car carrying a local security guard was shot at, according to Russian news agency TASS. The Caucasus region continues to be plagued by violence attributed to Islamic fundamentalists, separatists and organized crime.

Also on Saturday, several pro-Kremlin military bloggers reported that a Russian military aircraft, identified by one as a Su-34 fighter, had been shot down by Ukrainian forces. The incident has not been independently verified.

Russia has deployed 50,000 troops to the Kursk region in recent weeks to support an ongoing counteroffensive, according to Oleksandr Syrskyi, commander in chief of Ukraine’s armed forces.

Ukrainian forces launched a surprise attack on Kursk Province in August, capturing a number of towns and villages before the line could be stabilized by Russian reinforcements.