KIEV, Ukraine — Government troops ousted pro-Russian separatists and raised the national flag over a port city in the east and regained control over a stretch of the border with Russia, Ukrainian officials announced Friday.
The predawn attack on separatist strongholds in the city of Mariupol, the second-largest city in the Donetsk region, was over in less than six hours, according to the interior minister, Arsen Avakov. At least five separatists were reported killed and four Ukrainian soldiers were wounded.
Mariupol is considered strategically important because it is situated on major roads and because steel is exported through its port. Separatists have infiltrated Mariupol several times in the conflict, and full Ukrainian control may prove to be only temporary. But in a sign that Ukrainians expect to stay in charge, President Petro Poroshenko ordered Serhiy Taruta, the Donetsk governor who has been ruling from Kiev in recent weeks, to relocate to Mariupol.
After a series of setbacks, the battlefield victory underscores a growing confidence among Ukrainian officials that the tide may have turned in the conflict that has raged since April.
Poroshenko has called on the separatists to lay down their arms and said he will negotiate with anyone who doesn't have the blood of innocents on his hands. At the same time, the army has been increasingly aggressive in attacking separatists, who control a swath of the Donetsk and Luhansk regions, where they have proclaimed "People's Republics" and have asked for international recognition from several countries such as Russia and Venezuela.
Avakov also said Friday that government troops again controlled a 75-mile stretch of the 1,250-mile border that had been in the hands of insurgents.
An aide, Anton Gerashchenko, predicted that the entire border would be under Ukrainian control by this weekend.
The border, which was considered porous even before the conflict began, has been easily crossed by fighters and convoys bearing supplies.
On Wednesday, three seemingly old and decommissioned tanks rumbled through the Donetsk and Luhansk regions. Ukrainian officials said they came across the border from Russia, but Russia denied that.
On Friday in Washington, State Department officials said Russia had sent tanks and rocket launchers to the rebels. Department spokeswoman Marie Harf said the United States had information that Russia has accumulated tanks of a type no longer used by its own forces at a site in southwest Russia, and some had recently left that spot.
Information from the Associated Press was used in this report.