President Petro Poroshenko on Friday said a "real" ceasefire was in place in Ukraine after the first 24 hours in seven months without a military casualty, although he admitted the truce was fragile.

"I have positive news. Today is the first 24 hours for seven months... when we have a real ceasefire in Ukraine," he said in a speech during a trip to Australia.

"You simply can't imagine how important it is for me. This is the first night when I don't have either a lost or wounded Ukrainian soldier."

The ceasefire with pro-Russian rebels was introduced on Tuesday in the hope of ending an eight-month conflict that has claimed at least 4,300 lives and displaced close to one million people, according to United Nations figures.

A Ukrainian military spokesman said on Thursday that three soldiers were killed and eight injured in the day preceding his comments.

But Poroshenko said the last 24 hours had passed without incident and that if the ceasefire held it would be "a great step for peace and stability in Ukraine".

But he warned it had only been a day.

"Everything is so fragile. But I pray that we should continue this process," he said.

"And if we will be united we will win, no doubt. Not win by military means, but we will launch political dialogue, bring peace, bring stability to my nation, to the continent and to the whole world."

The process is being closely watched in Europe, where concerns over Russia's support for the rebels has plunged East-West relations to their lowest ebb since the end of the Cold War.

The two sides -- along with Russian and European monitors -- are still trying to organise comprehensive peace talks.

'We'll win Crimea battle'

Poroshenko added that the conflict in his homeland was not just about Ukraine's independence and territorial integrity.

"This is a war for freedom, global freedom. This is a war for democracy, global democracy and this is the war for security, global security," he said.

"And I think that the tragic events which happened in July in Ukraine's sky, the terrorist attack against MH17, demonstrated how close and how small is the world."

Some 298 people died, including 38 Australian citizens and residents, when Malaysia Airlines MH17 was downed in rebel-held eastern Ukraine.

The West has claimed the plane was blown out of the sky with a missile supplied by Russia, an allegation Moscow denies.

When asked about Moscow's annexation of Crimea in March, the Ukrainian leader said he was confident the territory would eventually be returned to his country.

"I have no doubt on that. Crimea is Ukrainian... I'm absolutely sure that we'll win the battle for the Crimea," he said.

"This is a brutal violation of international law. And there should be a responsibility for this violation."

Poroshenko added that he believed the Ukrainian conflict was a "very emotional" matter for Russian President Vladimir Putin, but that peace was possible.

"I think that the Ukrainian matter for him is very emotional... I avoid the term 'we will win war'. But I can use the term 'we will win peace'," he said.

Poroshenko was greeted by dozens of Ukrainian supporters following his speech in Sydney, snapping photographs with them and joining in a rendition of the national anthem.

One supporter, Ukrainian Oleksandra Krasnova, told AFP it was vital her country continued to receive support from the international community.

"The support makes Ukraine stronger and gives more faith and belief to the Ukrainian people. It's quite important in these difficult times," she said.