MONS, Belgium -- NATO Secretary-General Jens Stoltenberg has said that "Russia is still in Ukraine" and urged Moscow to withdraw all its forces and to end its support for separatists in eastern Ukraine.
Stoltenberg said on March 11 that NATO "has seen and still sees a strong Russian presence and strong support for separatist forces in eastern Ukraine."
U.S. General Philip Breedlove, the supreme allied commander of NATO troops, said at the same press conference in Mons, Belgium, that the alliance has "seen some success" with a cease-fire deal agreed in Minsk last month that has greatly reduced fighting and led to the withdrawal of some heavy weapons.
But Breedlove said it was "difficult to know" where the heavy weapons moved from the front line have been taken.
He added that the border between Russia and much of eastern Ukraine was wide open, making it difficult to monitor and hard to determine how many Russian troops are in Ukraine.
Breedlove said it was imperative that monitors from the Organization for Security and Cooperation in Europe (OSCE) be given full access and freedom of movement in eastern Ukraine to verify the withdrawal of heavy weapons.
Stoltenberg said that the "monitoring of the cease-fire is in no way sufficient today."
More than 6,000 people have been killed since April in fighting between Ukrainian government forces and Russian-backed separatists who have seized control of parts of the Donetsk and Luhansk regions in eastern Ukraine.
The conflict followed Russia's annexation of Crimea from Ukraine, a move Kyiv and the West say was illegal.
'Disappointment' On Treaty Pullout
Stoltenberg also expressed disappointment at Russia's decision to suspend its its participation in the Joint Consultative Group (JCG) on the Treaty on Conventional Armed Forces in Europe.
The decision was announced of Russia's Foreign Ministry website on March 10.
"We are disappointed by Russia's decision," Stoltenberg said on March 11.
Aleksandr Mazur, the head of the Russian delegation to Vienna talks about military security and arms control, said in the March 10 statement that Russia's participation in the advisory group was "meaningless from a political and practical point of view and an unjustifiable waste from a financial-economic [point of view]."
The statement noted Russia already suspended its participation the Treaty on Conventional Military Forces in Europe in 2007 saying NATO's expansion plans made it impossible to realize the terms of the treaty.
The statement said that with the decision to suspend its role in the JCG "the suspension of the CFE treaty announced by Russia in 2007 becomes complete."
Speaking more broadly, Stoltenberg said NATO was in the process of adapting its "defense posture" to new challenges caused by Russia in the east and along its southern flank due to "turmoil in the Middle East and North Africa."
Breedlove called the changes by NATO -- which include moving troops and military equipment to bases in Eastern Europe -- the "greatest change in our approach to collective defense since the Cold War."
In Kyiv, Ukrainian military officials said one soldier was killed and four wounded in the past 24 hours in fighting in eastern Ukraine.
A military spokesman said the casualties occurred near the rebel-held Donetsk airport and in the village of Shyrokyne, near the southeastern port of Mariupol, which is controlled by the government.
In Brussels, European Union diplomats told RFE/RL on March 10 that EU leaders may decide at a March 19 summit to keep economic sanctions against Russia in place though December in hopes of bolstering the implementation of the Ukraine peace deal.
The February 12 deal, brokered in Minsk by German Chancellor Angela Merkel and French President Francois Hollande in talks with Russian President Vladimir Putin and Ukrainian President Petro Poroshenko, calls for Ukraine's control over its border with Russia to be restored by the end of 2015 if other aspects of the agreement are implemented.
EU sanctions targeting the Russian energy and financial services sectors were agreed in June and July 2014 and will be up for renewal one year after they entered into force.
The sanctions, imposed over Russia's annexation of Crimea and support for separatists fighting government forces in eastern Ukraine, will expire without a unanimous decision to extend them.
With reporting by Rikard Jozwiak and AFP