By Kanupriya Kapoor

SINGAPORE (Reuters) -Indonesia's defence minister on Saturday proposed a peace plan to end the war in Ukraine, calling for a demilitarised zone and a United Nations referendum in what he called disputed territory.

Ukrainian foreign ministry spokesperson Oleg Nikolenko dismissed the plan, reiterating Kyiv's position that Russia should withdraw its troops from Ukraine.

Prabowo Subianto called on defence and military officials from around the world, gathered at the Shangri-La Dialogue defence meeting in Singapore, to issue a declaration calling for a cessation in hostilities.

He proposed a multi-point plan including a ceasefire and establishing a demilitarised zone by withdrawing 15 kilometres (nearly 10 miles) from each party's forward position.

The demilitarised zone should be observed and monitored by a peacekeeping force deployed by the UN, he said, adding that a UN referendum should be held "to ascertain objectively the wishes of the majority of the inhabitants of the various disputed areas".

"I propose that the Shangri-La dialogue find a mode of ... voluntary declaration urging both Ukraine and Russia to immediately start negotiations for peace," Prabowo said.

Nikolenko said Russia had committed the act of aggression, occupying Ukrainian territories, and any proposals for a ceasefire would allow it to regroup and reinforce.

"There are no disputed territories between Ukraine and the Russian Federation to hold referendums there," he said.

"In the occupied territories, the Russian army commits war crimes, crimes against humanity and genocide. Russia is now trying in every possible way to disrupt the Ukrainian counteroffensive."

Russia has denied Ukrainian accusations of war crimes and genocide.

Indonesia's proposal follows President Joko Widodo's visit last year to Moscow and Kyiv, where he offered to play peacebroker between their leaders and rekindle peace talks. He was chairman of the G20 group of major economies at the time.

Speaking on the same panel, Josep Borrell Fontelles, high representative and vice president of the European Union's European Commission, noted that if military support for Ukraine stopped, the war would quickly end - but with that country's sovereignty falling to outside aggression.

"We cannot stop supporting militarily Ukraine because we don't want the peace which is ... the peace of the surrender. The peace of the stronger," Borrell said.

Ukrainian President Volodymr Zelenskiy has proposed a 10-point peace plan which calls on Russia to withdraw all its troops from Ukraine. Nikolenko urged Indonesia to support Zelenskiy's peace plan.

(Reporting by Kanupriya Kapoor; Additional reporting by Olena Harmash in Kyiv; Editing by Gerry Doyle and David Holmes)