Russian forces destroyed key infrastructure in Ukraine’s southern city of Kherson before fleeing, President Volodymyr Zelenskiy said, as his counterparts in Russia and Iran vowed to deepen economic, political and trade ties.

Zelenskiy described as hellish battles in the eastern region of Donetsk, where pro-Moscow forces were putting up a much stiffer fight after Russia abandoned on Friday the only regional capital it had captured since the war began in February.

Jubilant residents of Kherson welcomed arriving troops while Zelenskiy said authorities, in their efforts to stabilise the region, had dealt with nearly 2,000 mines, trip-wires and unexploded shells left by the departing Russians.

Russians “everywhere have the same goal: to humiliate people as much as possible. But we will restore everything, believe me,” Zelenskiy said in a video address on Saturday.

“Before fleeing from Kherson, the occupiers destroyed all the critical infrastructure: communications, water, heat, electricity.”

Ukraine’s success in Kherson, where its troops now control more than 60 regional settlements, as well as in other places, benefited partly from resistance in the Donetsk region, despite repeated Russian attacks, Zelenskiy added.

“There it is just hell - there are extremely fierce battles there every day,” he said. “But our units are defending bravely - they are withstanding the terrible pressure of the invaders, preserving our defence lines.”

In a telephone call, Russian President Vladimir Putin and Iranian President Ebrahim Raisi emphasised “further enhancing cooperation in the political, trade and economic fields, including the transport and logistics sector,” the Kremlin said on Saturday.

Russia has stepped up efforts to build ties with Iran and other non-Western countries during the war, with a senior Russian security official having met Iranian leaders in Tehran on Wednesday.

The visit followed accusations by Ukraine and the West that Russia has used Iranian drones to target Ukraine’s energy infrastructure.

Iran says it sent Russia a small number of drones before the war began. Last month, two senior Iranian officials and two Iranian diplomats told Reuters that Iran had promised to provide Russia with surface-to-surface missiles.

But Ukraine will decide on the timing and contents of any negotiation framework with Russia, according to the readout of a Saturday meeting between US Secretary of State Antony Blinken and Ukrainian Foreign Minister Dmytro Kuleba in Phnom Penh.

The Washington Post reported a week ago that the Biden administration was privately encouraging Ukraine's leaders to signal an openness to negotiate with Russia and drop their public refusal to engage in peace talks unless Putin was removed from power.

Moscow calls its action in Ukraine a “special military operation” aimed at demilitarizing and “denazifying” its smaller neighbour. Kyiv and its allies say Russia’s invasion, which has killed tens of thousands and uprooted millions, was unprovoked and illegal.