The commanders of two Ukrainian units defending the besieged port city of Mariupol issued a video statement saying they had been able to join forces, as Russia claimed advances in the city.

Their statement comes as Ukrainian forces remain blockaded inside Mariupol, which has been under weeks of relentless bombardment. The Russian military has repeatedly claimed to have taken strategic positions in the city, but has also faced stiff resistance from Ukrainian forces.

Denys Prokopenko, the commander of the Azov Regiment, said his unit had linked up with troops from the 36th Marine Brigade, but acknowledged that some Ukrainian defenders had surrendered. 

“These are real men [of the 36th] who have chosen the path of war,” he said. “Do not make heroes out of deserters and fighters who voluntarily surrendered. They chose the path of shame, and shouldn’t be heroized in any case.”

Ukrainian presidential adviser Oleksiy Arestovych had said earlier on Wednesday that after a “risky maneuver” the last remaining defenders of the besieged port city of Mariupol have been able to join forces.

“This is what happens when officers do not lose their heads, but firmly maintain command and control of the troops,” Arestovych said.

CNN cannot independently confirm the details of the operation. 

Meanwhile, in a statement Wednesday, Russian Ministry of Defense spokesperson Maj. Gen. Igor Konashenkov said Mariupol’s commercial seaport had been captured. CNN was not independently able to verify that claim.