Report: Putin wants delay in referendum in Ukraine's Donetsk regionMARIUPOL, Ukraine (CNN) -- Russian President Vladimir Putin wants a delay in a referendum on whether certain eastern Ukrainian residents want sovereignty from Ukraine, Russian government news agency ITAR-Tass reported Wednesday.
By: Arwa Damon, Lena Kashkarova and Laura Smith-Spark, CNN
MARIUPOL, Ukraine (CNN) -- Russian President Vladimir Putin wants a delay in a referendum on whether certain eastern Ukrainian residents want sovereignty from Ukraine, Russian government news agency ITAR-Tass reported Wednesday.
Separatists in Ukraine's Donetsk region earlier scheduled a referendum for Sunday.
Putin, speaking after a meeting in Moscow with the chairman of the Organization for Security and Co-operation in Europe, called for a delay Wednesday "to create proper conditions for this dialogue," ITAR-Tass reported.
In March, voters in Ukraine's Crimea Peninsula approved a controversial referendum to secede from Ukraine and join Russia, which subsequently annexed the Crimea region. That event highlighted the turmoil rocking Ukraine.
Meanwhile, NATO has "no indication" that Russia has moved its troops from the Ukrainian border, a NATO military official said Wednesday on condition of anonymity.
That comment came after Putin said Wednesday, after a meeting with OSCE chairman Didier Burkhalter, that Russian forces are "now not on the Ukrainian border but are carrying out their regular exercises at the test grounds."
Elsewhere, five pro-Russian activists were killed overnight when Ukrainian forces attacked barricades on the outskirts of Ukraine's southeastern city of Mariupol, a spokeswoman for the pro-Russian camp said Wednesday.
Ukrainian forces detained 15 other activists, Irina Voropaeva said.
The violence comes amid an escalation of tensions as Ukrainian forces seek to regain control of some of the administrative buildings seized by pro-Russian separatists in a swath of the country's south and east.
The activists briefly abandoned the Mariupol City Council building, according to Voropaeva.
But the security forces remained in the building for only a short time, saying they had been ordered to leave.
The activists re-entered and Russian and regional flags went back up, to the cheers of the crowd outside.
Later Wednesday, witnesses told CNN that Ukrainian forces dressed in black had fired over the heads of separatists who had gone to a Mariupol police station to demand the release of the 15 detained activists.
The witnesses said several people were taken away in ambulances.
Elsewhere in the volatile Donetsk region, an uneasy standoff continued Wednesday between the Ukrainian military and the separatists.
Both sides clashed at the rebel stronghold of Slovyansk on Monday. Ukraine's security services said 30 "heavily armed" militants had been killed in recent days as part of the "anti-terrorist" operation in the area.
As the tensions rise, uncertainty reigns.
The eastern Donetsk and Luhansk regions said they would hold a referendum on autonomy Sunday, but there are no visible preparations for a vote.
In Kiev, the interim government plans to hold presidential elections on May 25, but it acknowledges it has lost control of part of the country.
Russian Foreign Minister Sergey Lavrov on Tuesday said it would be "unusual" to hold a presidential election in the country when the army was being deployed against the population.
In what could be a sign of Moscow preparing to question the legitimacy of the May 25 election if it is unhappy with the process, Lavrov said: "In the situation where they use the army against their own population, it's quite unusual."
"This is not Afghanistan; this is a completely different situation," he said, adding that constitutional reforms promised by Kiev's new leaders would not be implemented in time for the vote.
Lavrov, speaking after a meeting of Council of Europe foreign ministers in Austria, also ruled out holding a second international meeting in a bid to defuse the crisis in Ukraine, saying that the provisions of a first international pact signed in Geneva, Switzerland, last month had yet to be put into force.
The agreement called on all parties to refrain from violence, as well as saying illegal armed groups must disarm and vacate seized public buildings.
Ahead of talks with Burkhalter, the OSCE chairperson-in-office for 2014, regarding Ukraine, Putin said Wednesday: "I know that you have your own proposals, your ideas of how to find a way out of the situation that has occurred. Our position is known too.
"Let's try to analyze the situation and seek ways out of this crisis," he added.
Kiev and many in the West believe that the separatists are backed by Moscow and fear that Putin is fomenting trouble to increase his influence in the region.
Crimean voters passed their referendum in March, and Russia subsequently annexed the peninsula, all while armed pro-Russian groups, backed by Russian forces, controlled key infrastructure.
But Moscow says that right-wing, ultranationalist groups are behind the violence in Ukraine and that it has no direct influence over the pro-Russian groups.
The rising tensions could have an impact far beyond Ukraine's borders, NATO Secretary General Anders Fogh Rasmussen warned Tuesday.
"Today we are facing the gravest crisis to European security since the end of the Cold War," he told reporters.
"But this is not just about Ukraine. This crisis has serious implications for the security and stability of the Euro-Atlantic area as a whole."
CNN's Arwa Damon reported from Mariupol and journalist Lena Kashkarova from near Donetsk, while Laura Smith-Spark wrote from London. CNN's Marie-Louise Gumuchian, Claudia Rebaza, Olga Pavlova, Kellie Morgan and Michael Martinez contributed to this report.