The government of Ukraine has announced it has reached a cease fire agreement with separatist rebels in the eastern part of the country. It will go into effect at 10:00 AM eastern time and will be monitored by the European security agency, the OSCE.

But after the announcement, rebels continued to pound the key port city of Mariupol, and there are reports that armor has entered the city.

New York Times:

The announcement had been expected, after both Mr. Poroshenko and President Vladimir V. Putin of Russia said earlier this week that they expected a truce to emerge from the talks in Minsk.

The agreement consisted of 14 points, including the exchange of hostages, according to an initial news bulletin from the Interfax Ukraine news agency before the official announcement from the envoys involved.

Mr. Putin offered an outline for a cease-fire agreement on Wednesday before the talks began, starting with “end active offensive operations” on both sides, that he said he hoped would be accepted by all parties at the talks.

His plan included a call for Ukrainian artillery to pull back out of range of the eastern separatists’ strongholds; an end to airstrikes; an exchange of all captives; the opening of humanitarian corridors for residents of the separatist areas; repairing damaged infrastructure; and deploying international observers to monitor the cease-fire.

Ukraine and many Western observers have accused Russia of backing the rebels with fighters and matériel, and of moving its own troops into Ukrainian territory to support the rebels. Mr. Putin and his government have denied those accusations and insisted that Russia is not a party to the conflict.

Welcoming Mr. Putin’s proposal, Mr. Poroshenko said when the talks began in Minsk that Ukrainian soldiers would observe a cease-fire agreement. Some separatist leaders said they would respect it, but others rejected it. The separatists also demanded that all Ukrainian forces withdraw completely from the disputed area.

The Ukrainian military spokesman, Col. Andriy Lysenko of the National Security and Defense Council, said on Friday that Russian-backed forces were moving tanks, artillery and other heavy equipment toward the village near Mariupol, and that Russia was also beginning to mass troops along the neck of land connecting the rest of Ukraine with the Crimean peninsula, which Russia annexed in March. The colonel said the movements were meant to threaten Mariupol from two sides.

The Russian state-run news agency RIA Novosti quoted unidentified separatist sources as saying that a group of its armored vehicles had entered Mariupol, but Colonel Lysenko denied the report, saying government forces were fully in control of the city.

There is some reason to doubt that all separatist groups will abide by the cease fire. There are several power centers in the separatist movement, and rivalries and personality conflicts have roiled negotiations in the past. There is also the possibility that Putin could encourage continued fighting around Mariupol in order for separatist forces to sieze that strategic port.

So a wise attitude to take about this cease fire is, "I'll believe it when I see it."