(CNN) Peace in eastern Ukraine remains tenuous as a spate of violations of a newly implemented ceasefire continued into Wednesday.

A day after the head of the Organization for Security and Co-operation in Europe (OSCE) warned the ceasefire had failed, German Foreign Minister Sigmar Gabriel urged Kiev and Moscow to hold fast to the agreement.

Despite assurances given by both parties, he said, the "ceasefire is not holding."

"We can only urgently appeal to both sides to implement the agreements we have reached -- otherwise, we will risk an intensified military escalation with many other civilian victims and a continuation of the standstill in the political process," Gabriel said in a statement.

"Even the most intense negotiating efforts are in vain when there is no political will to implement them."

Both sides had agreed to the withdrawal of "heavy weapons and full compliance" with the ceasefire, which was supposed to start Monday, Gabriel said.

At the United Nations

Speaking Tuesday at the headquarters of the United Nations, OSCE Secretary General Lamberto Zannier revealed there had been "no signs of the withdrawal of the weapons."

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"The crisis in and around the Ukraine continues to be a major source of tension and instability in Europe," he said.

Zannier had been invited by the Ukraine delegation of the Security Council to speak before the chamber.

He told the Security Council that the OSCE was "monitoring the ceasefire and are ready to observe the much-needed withdrawal of heavy weapons."

Continued violations

Zannier told reporters that there continued to be a number of violations and that the impact on civilians in the disputed regions was becoming "increasingly significant."

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"We will need to keep pushing and activate the international community also to put pressure on the sides to implement" steps to ensure the ceasefire holds.

His appearance came just before the organization's principle deputy chief monitor told CNN that there were about 200 ceasefire violations overnight Tuesday local time. The number is in addition to hundreds more observed since the ceasefire nominally began Monday.

Alexander Hug, principle deputy chief monitor of the OSCE's special monitoring mission to Ukraine, told CNN's Clare Sebastian that about 100 of those violations were explosions, indicating that heavy weaponry, such as tanks and mortars, is still in place.

Unlike the last few weeks, when critical infrastructure was cut off, there is no immediate crisis as of now, but any of these explosions could knock out a power line and make things worse, Hug added.

Zannier said relations between the West and Russia remain "strongly adversarial" and that "in Europe, we increasingly see the impact of an approach to the post-Cold War phase (of cooperation) with a Cold War mentality."

Zannier: Putin moves jeopardize framework

Zannier said there was a "very real risk of escalation" in fighting in the region and that Russian President Vladimir Putin's executive order to recognize travel documents from the de facto, pro-Russian separatist authorities in disputed areas of eastern Ukraine "complicates the implementation of the Minsk agreement."

The latest ceasefire is a renewed attempt to enforce the Minsk peace protocol -- the framework for peace in the region that has repeatedly failed since it was first partially implemented two years ago.

Putin effectively withdrew from the Minsk agreement last week by signing an executive order recognizing travel documents issued by separatist authorities in the region.

Putin spokesman Dmitry Peskov has said Russia is recognizing the travel documents "for humanitarian reasons."

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But at a Security Council briefing Wednesday, the Ukrainian delegation said Russia isn't fully living up to its end of the deal.

"Instead of full and good-faith implementation of the Minsk commitments, Russia resorts to political and military provocations, blackmail and political pressure," the delegation said in a statement.

In addition, Ukraine said, the Trilateral Contact Group -- representatives of Ukraine, Russia and OSCE -- "should pay particular attention to achieving immediate and unconditional release of Ukrainian citizens, who remain illegally detained as hostages or political prisoners in the occupied areas of Donbas and in Crimea, as well as in the Russian Federation."

What is the Minsk agreement?

The Minsk agreement, which was negotiated in 2014 but never fully implemented, calls for the "bilateral cessation of the use of all weapons," and the decentralization of power in the region "with respect to the temporary status of local self-government in certain areas of the Donetsk and the Lugansk regions."

At the time, then-Ukrainian Prime Minister Arseniy Yatsenyuk spoke of the deal with guarded optimism.

"We had just two options: bad, and worse," he said. "So we decided at this particular period of time to get the bad option. Probably this option will save the lives of Ukrainian soldiers, and I hope this option will save lives of Ukrainian civilians, of innocent people, who are under a constant shelling of Russian-led terrorists."

"It's better to have this new deal rather than not to have (it)," he said. "But we do not trust any words or any papers. We are to trust only actions and deeds."