horrible photos of those burned in #Odessa http://t.co/569XhsWdLo. notice some were shot and others were lying in rooms untouched by fire
— Kateryna_Kruk (@Kateryna_Kruk) May 5, 2014
Ukrainian Interior Minister Arsen Avakov was quoted as saying that there have been "deaths" as troops fight pro-Russian militants who control the city.
Rebel forces were reportedly withdrawing toward the center of the city after government forces took control of a television tower in the southern suburb of Andreyevka.
Slovyansk, a city of some 140,000 is one of a string of cities in eastern Ukraine controlled by pro-Russian rebels.
The government has vowed to continue an "antiterrorist" operation until it regains control.
Acting President Oleksandr Turchynov has said Russia "is at war" with his country.
Russia denies the Ukrainian government's accusations that it is fomenting violence in southern and eastern Ukraine.
Ukraine formally closes border checkpoints in occupied Crimea. Russian media reports: "Ukraine seals off its border".
— Leonid Ragozin (@leonidragozin) May 5, 2014
Reports of heavy fighting on the #Slovyansk outskirts today. Unconfirmed vid of huge explosion seen there https://t.co/enTcUYmDaF
— Maxim Eristavi (@MaximEristavi) May 5, 2014
Ukrainian flag still in front of Trade union building #Odessa @Ruptly #Ukraine pic.twitter.com/N9SPHjkuUh
— Katica Djurovic (@zoontangmarg) May 5, 2014
#Ukraine the face of grief. Funeral for 20 yr old woman in #Kramatorsk Mourners blame army pic.twitter.com/5HKJMAbTDb
— Fergal Keane (@fergalkeane47) May 5, 2014
"The television tower, which is located in the village of Andreyevka in the suburb of Slovyansk, has been taken over by the enemy. Fighting is going on in Andreyevka and Semyonovka. We currently have to retreat inside, behind the city line. The enemy is already on the territory of Slovyansk," the source said.
Several people were wounded during the night fighting. According to some reports, a young girl was killed.
Interfax currently has no official confirmation of the information on the people hurt in the fighting from the Ukrainian law enforcement agencies
Turkish Hurriyet's today world section issue headline reads "Putin's Prosecutor declared war on Crimea Tatars" pic.twitter.com/U4Npc5usWk
— Ryskeldi Satke (@RyskeldiSatke) May 5, 2014
#Slavyansk: Reports emerge of battle taking place near TV station in the city. No causalities registered.
— PaulaSlier_RT (@PaulaSlier_RT) May 5, 2014