Following witness reports of loud artillery explosions near the Ukrainian city of Donetsk, the country's President Petro Poroshenko modified his statement to remove the word "permanent". It is unclear whether his actions were in response to reports of the explosion.
Comment: Poroshenko says one thing on one day, and something completely contradictory the next, so it's anyone's guess what his real intentions are. But if past events are any indication, he'll probably just continue to bomb civilians in Novorossiya until someone else stops him.
Reporting from Mariupol, Ukraine, Sky's Moscow Correspondent Katie Stallard said: "It's extremely unclear at this stage what exactly this ceasefire is supposed to be. No one we have spoken to on the ground seems to know about it.
"The Ukrainian president issued a statement this morning claiming he agreed with Vladimir Putin to a permanent ceasefire in the region. He has since slightly modified that statement and removed the word 'permanent'. A spokesman for President Putin said no such agreement has been reached, nor can it, because Russia is not a party to the conflict."
Mr Putin's spokesman Dmitry Peskov was earlier quoted as saying the leaders' views "overlap to a considerable degree".
"The heads of state exchanged opinions about what needs to be done first in order to bring an end to the bloodletting in the southeast of the country as soon as possible," said Mr Peskov.
A statement from Kiev said an understanding had been achieved which would enable the "establishment of peace".
News of the development was greeted with an immediate rally on the financial markets - the main Russian stock exchange, the Micex, rising 4% and stocks in London with the FTSE 100 reached a 14-year high in morning trade.
Russia later announced it was to hold major military exercises in September of the forces responsible for its long-range nuclear capability. The drills will involve more than 4,000 servicemen and 400 technical units.
Meanwhile, world leaders have begun arriving in the UK ahead of a two-day Nato summit in Wales where the Ukraine crisis will be top of the agenda.
Speaking in Estonia ahead of the summit, President Obama said that Nato would not accept what he called Russia's illegal annexation of Crimea.
In a thinly-veiled warning to President Putin, the US President added that the Baltic states were bound by the Nato alliance.
"We have a solid duty to each other. Article Five is crystal clear; an attack on one is an attack on all," he said.
Mr Obama added the US was working to bolster the security of Nato allies and increase America's military presence in Europe.
"It would mean more US forces, including American boots on the ground continuously rotating through the Estonia, Latvia and Ukraine militaries."
Russia has repeatedly denied claims its soldiers were recently sent into eastern Ukraine to support Ukrainian pro-Russian rebels.