Russia took aim at Western military supplies for Ukraine on Sunday, launching strikes on Kyiv as Vladimir Putin warned that any Western deliveries of longer-range rocket systems would prompt Moscow to hit "objects that we haven't yet struck".

The Russian leader's threat of military escalation did not specify what the new targets might be. It came days after the United States announced plans to deliver 700 million dollars (£560 million) of security assistance for Ukraine that includes four precision-guided, medium-range rocket systems, as well as helicopters, Javelin anti-tank systems, radars, tactical vehicles and more.

The UK also announced it will send its first long-range missiles to Ukraine. Defence Secretary Ben Wallace said Britain will send an unspecified number of M270 launchers, which can fire precision-guided rockets up to 50 miles - a longer range than any missile technology currently in use in the war.

In a television interview that aired on Sunday, Mr Putin lashed out at Western deliveries of weapons to Ukraine, saying they aim to prolong the war.

"All this fuss around additional deliveries of weapons, in my opinion, has only one goal: To drag out the armed conflict as much as possible," Mr Putin said.

He insisted such supplies were unlikely to change the military situation for Ukraine's government, which he said was merely making up for losses of similar rockets.

If Kyiv gets longer-range rockets, he added, Moscow will "draw appropriate conclusions and use our means of destruction, which we have plenty of, in order to strike at those objects that we haven't yet struck".

The missiles that struck Kyiv destroyed T-72 tanks supplied by eastern European countries and other armoured vehicles, the Russian Defence Ministry said on the Telegram app.

Ukraine's railway authority led reporters on a guided tour of a rail car repair plant in eastern Kyiv that it said was hit by four missiles. The authority said no military equipment had been stored there, and Associated Press reporters saw no remnants of any in the facility's destroyed building.

"There were no tanks, and you can just be witness to this," said Serhiy Leshchenko, an adviser to the Ukrainian president's office.

However, a government adviser said on national TV that military infrastructure was also targeted. AP reporters saw a building burning in an area near the destroyed rail car plant.

Two residents of that district said the warehouse-type structure that billowed smoke was part of a tank-repair facility. Police blocking access to the site told an AP reporter that military authorities had banned the taking of images there.

The US has stopped short of offering Ukraine longer-range weapons that could fire deep into Russia. But the four medium-range High Mobility Artillery Rocket Systems in the security package include launchers on wheels that allow troops to strike a target and then quickly move away - which could be useful against Russian artillery on the battlefield.

Moscow also accused the West on Sunday of closing off lines of communication by forcing Foreign Minister Sergey Lavrov's plane to cancel a trip to Serbia for talks on Monday.

Serbia's neighbours closed their airspace to Lavrov's plane, ministry spokeswoman Maria Zakharova told Italian television in comments reported by Russian news agencies. Earlier in the day, Serbian newspaper Vecernje Novosti had said that Bulgaria, North Macedonia and Montenegro would not allow Mr Lavrov's plane to come through.

"This is another closed channel of communication," Ms Zakharova said.

The Spanish daily El Pais reported on Sunday that Spain planned to supply anti-aircraft missiles and up to 40 Leopard 2 A4 battle tanks to Ukraine. Spain's Ministry of Defence did not comment on the report.

Before Sunday's early morning attack, Kyiv had not faced any such Russian airstrikes since the April 28 visit of UN Secretary-General Antonio Guterres. The attack triggered air-raid alarms and showed that Russia still had the capability and willingness to hit at Ukraine's heart, despite refocusing its efforts to capture Ukrainian territory in the east.

In recent days, Russian forces have focused on taking Ukraine's eastern cities of Sievierodonetsk and Lysychansk. On Sunday they continued their push, with missile and airstrikes on cities and villages in the Donbas.

In the cities of Sloviansk and Bakhmut, cars and military vehicles were seen speeding into town from the direction of the front line. Dozens of military doctors and paramedic ambulances worked to evacuate civilians and Ukrainian servicemen, and a hospital was busy treating the injured, many hurt by artillery shelling.

The UK Ministry of Defence (MoD) said in its daily intelligence update that Ukrainian counterattacks in Sieverodonetsk were "likely blunting the operational momentum Russian forces previously gained through concentrating combat units and firepower". Russian forces previously had been making a string of advances in the city, but Ukrainian fighters have pushed back in recent days.

The statement also said Russia's military was partly relying on reserve forces of Luhansk separatists.

"These troops are poorly equipped and trained, and lack heavy equipment in comparison to regular Russian units," the intelligence update said, adding that the move "indicates a desire to limit casualties suffered by regular Russian forces".