The tactic may have been introduced by veterans of separatist conflict in Chechnya.
Russia's army is attacking Ukrainian forces with explosive-laden old vehicles, the UK Ministry of Defence has said.
In a Thursday intelligence briefing, it noted several reports that Russian forces were using "antiquated armoured vehicles packed with several tonnes of explosives as vehicle-borne improvised explosive devices".
These vehicles are then set on course to the Ukrainian frontline, with the crew likely bailing out, the MoD explained.
It claimed there is a "realistic possibility" that this tactic is the work of Chechen forces.
Chechens are among a few groups fighting on both sides in the Ukraine war, hailing from a restive semi-autonomous region in the Caucasus.
Many of those fighting for Russia teamed up with Moscow to break the rebellion of their own people during the Second Chechen War, which lasted from 1999 to 2009.
A Euronews report from May found that Russia has used Chechens to discipline and reportedly even execute dissenting soldiers, as well as to intimidate civilians in Ukraine.
Many Chechens fighting on Kyiv's side – including some radical Islamists – fought against Moscow during past separatist wars.
The UK MoD noted that most of the vehicle IEDs had been reportedly used in Donetsk, near Marinka, with practice appearing days after Chechen units "skilled in IED use" were sent to the area.
Chechens waging war for Ukraine also reportedly used similar explosive devices in January 2023.
The UK MoD questioned the "viability" of this tactic, saying most of the devices detonate before they reach their target.
Nonetheless, the ministry pointed out that they cause "extremely loud explosions, which are still likely to have a psychological effect on defending forces".
Chechen men fighting under Russia’s flag are known as the Kadyrovtsy, after the father of the leader of the Chechen Republic, Ramzan Kadyrov, often referred to as “Putin’s mad dog”.
“They are like his personal army,” Harold Chambers, a North Caucasus analyst, told Euronews in May.
He explained that a “big reason” why they are in Ukraine is because Kadyrov, a staunch advocate of the war, wants to curry favour with the Russian president.