A Ukrainian military helicopter was shot down near the pro-Russian rebel-controlled eastern town of Slaviansk on Monday, but the pilots survived, the Defense Ministry said.
The helicopter, an Mi-24, which came under fire from a heavy machine gun, crashed into a river. The ministry said in a statement the crew were evacuated to a nearby camp but did not give any detail of their condition.
At least three other helicopters have been shot down by pro-Russian rebels since uprisings began in eastern parts of the country early this year.
Earlier, Ukraine's Interior Minister said he had drafted a new special forces unit into the southern port city of Odessa after the "outrageous" failure of police to tackle pro-Russian separatists in a weekend of violence that killed dozens.
Fighting continued near the eastern city of Slaviansk where Ukrainian troops have been, somewhat tentatively, pressing a campaign to end pro-Russian rebellion. A Reuters correspondent said gunfire seemed to be coming closer to the city center.
The violence in Odessa, a southwestern port with a broad ethnic mix from Russians and Ukrainians to Georgians and Tatars, is seen as something as a turning point in Kiev; a warning of dangers if rebellion spreads beyond the Russian-speaking east.
Interior Minister Arsen Avakov said the new Odessa force was based on "civil activists who wanted to help the Black Sea city "in these difficult days". The entire leadership of the local police had been sacked and could face criminal action.
The Odessa violence was the deadliest since Moscow-oriented president Viktor Yanukovich fled to Russia in February and pro-Russian militants launched uprisings in the industrial east.
Ukrainian leaders have made it clear they see the police force across wide areas of the country as unreliable in the face of rebellion they say is backed by Moscow and led on the ground by Russian special forces. The units Avakov referred to emerged partly from the uprising against Yanukovich early this year.
That could fuel anger among the government's opponents, who accuse it of promoting "fascist" militant groups, such as Right Sector, which took part in the Kiev uprising over the winter.
Loss of control of Odessa would be a huge economic and political blow for Kiev, which accuses Moscow of scheming to dismember Ukraine, a country the size of France.
Odessa, a city of a million people, with a grand history as the cosmopolitan southern gateway for the tsars' empire, has two ports, including an oil terminal, and is a key transport hub.
It would also heighten Western concern that Ukraine, already culturally divided between an industrial, Russian-speaking east and a more westward looking west, could disintegrate. As well as humanitarian problems that could entail, neighboring NATO and EU countries would face a deep crisis in relations with Moscow, which supplies much of Western countries' energy via Ukraine.
Kiev's anger on Monday focused on the Odessa police decision to release 67 largely pro-Russian militants after supporters besieged and stormed a police station on Sunday.
The crowd of several hundred chanted "Odessa is a Russian city!" Russian is the first language of many of its residents.
The militants had been arrested on Friday after hours of clashes, with the use of petrol bombs and small arms, on the streets of the Black Sea city. Pro-Russian supporters withdrew to a building that later burnt down with the loss of over 40 people - bloodshed that Moscow blames on Kiev's "provocations".
Avakov said other detainees had been transferred away from Odessa in the night to more central areas of Ukraine to prevent any premature release.
Russian President Vladimir Putin and German Chancellor Angela Merkel discussed the Ukraine crisis in a telephone call and stressed the importance of "effective international action" to reduce tension, the Kremlin said on Sunday.
A German government spokeswoman said they had also discussed a visit to Moscow on Wednesday by the head of the OSCE, the European security body which has been trying to mediate on the ground but saw some of its monitors held for a week by rebels.
Addressing hundreds of supporters of the Kiev authorities who gathered near the site of the blaze late on Sunday, newly appointed police chief Ivan Katerinchuk promised to bring those behind Friday's deaths to justice, whatever their allegiance.
NATO commanders have said Russia might hope to control a swathe of southern and eastern Ukraine, including the annexed Crimea peninsula, all the way to the border with Transdniestria, the breakaway, pro-Moscow sliver of Moldova, just 50 km (30 miles) from Odessa, which is home to a Russian military base.
As well as crippling Ukraine, this would secure Russia additional warm water ports.
Kiev is organizing a presidential election for May 25.
However, as things stand, it would have trouble conducting the vote in many parts of the east, a circumstance that would allow Russia to declare any government emerging as bereft of legitimacy.
Russia denies ambitions to seize eastern Ukraine as it has annexed the Crimea peninsula but reserves the right to send troops to defend Russian-speakers if it deems necessary.
Separatists who have declared a "People's Republic of Donetsk" are planning a referendum on secession next Sunday.
The capital Kiev has remained quiet since the protests that forced Yanukovich to flee to Russia. But celebrations this week marking the anniversary of the Soviet victory in World War Two could be a source of tension.
REUTERS