The port, recently occupied by Russian forces with several Russian warships in dock, was rocked by a series of heavy explosions just after dawn.
Social media videos showed fires raging at the port, with a series of secondary explosions echoing across the city.
Ukraine’s armed forces said they “destroyed a large landing ship” which they named “Orsk”.
According to Russian media reports from the port, several Russian ships had unloaded military equipment in Berdyansk in the past few days.
Ukrainian forces said that in addition to destroying the Orsk, two other ships were damaged.
“A 3,000-ton fuel tank was also destroyed. The fire spread to the enemy ammunition depot. Details of the damage inflicted on the occupier are being clarified,” they said.
It is not known what weapon was used to attack the port.
This was shown by an analysis of the videos uploaded on Thursday One Russian Navy ship remains the port shortly after the explosions.
The Russian Defense Ministry had previously reported that “the large landing ship Orsk is the first warship of the Russian Federation to enter the port of Berdyansk. It has delivered equipment – armored personnel carriers.”
“The ships of this project are very spacious and can take on board a large amount of equipment, up to 20 tanks or up to 40 armored personnel carriers,” the ministry said.
Berdyansk is located on the Azov Sea and about 70 kilometers southwest of Mariupol. The city has a small naval base and a population of about 100,000.
Russian military forces occupied government buildings in Berdyansk for the first time on February 27, three days after the start of the Russian invasion.
CNN’s Tim Lister and Olga Voitovych reported from Lviv, Celine Alkhaldi from Abu Dhabi and Gianluca Mezzofiore from London.