Trump urges Ukraine army to stop hitting Russian diesel

US President Donald Trump has called on Ukrainian President Volodymyr Zelenskiy's military to stop targeting Russian diesel infrastructure, saying the attacks are causing a shortage of the fuel that is "hurting the world".

A wave of long-distance Ukrainian drone attacks on Russian oil refineries in recent months has reduced that country's fuel production, triggering petrol shortages across the country.

Ukraine, which faces regular Russian attacks on its own energy infrastructure, says refineries are legitimate military targets.

The US national average price for diesel, which is used by trucks, trains, ships and farm equipment, rose above $US6 a gallon ($A2.21 per litre) for the first time on Thursday, according to price tracker GasBuddy.

"Mr Zelenskiy has to do one thing: he has to stop knocking out diesel fuel in Russia," Trump told journalists during a visit to the Irish Open, which is being held in the west of Ireland on a golf course owned by his family.

"We spoke to Mr Zelenskiy about it. There are plenty of other targets. Don't hit diesel fuel. That's hurting the world," he said.

The global shortage "isn't done by the Middle East, this is done by what's happening with Russia and Ukraine," Trump added.

Russia downgraded oil output forecast for this year to a 17-year low and revised its fuel exports outlook for 2026 and 2027 due to the war, according to a government draft forecast seen by Reuters.

Local Russian officials in Tatarstan said on Sunday two people were killed in a Ukrainian drone attack while Ukrainian authorities reported Russian drone attacks on the Black Sea port of Odesa.

Two people were killed and 14 more injured on Sunday as Ukrainian drones struck Nizhnekamsk, a city in Tatarstan, according to the office of regional head Rustam Minnikhanov.

The two civilians died after a drone slammed into a tree near their parked car, the statement staid.

Nizhnekamsk houses a key cluster of oil refineries and petrochemical, rubber and polymer plants, including some of Russia's largest facilities of their kind.

Mayor Radmir Belyaev said that a fire had broken out "at one of the city's enterprises," without giving details.

At least nine people were injured in a "massive" Russian attack on Odesa, according to Serhii Lysak, who heads the city's military administration.