The situation in Ukraine's southeastern port city of Mariupol is "extremely difficult" but the city has not been taken under full control by Russian forces, a spokesman for Ukraine's defense ministry said on Monday.

Speaking at a media briefing, spokesman Oleksandr Motuzyanyk also said that bombing runs by Russian military aircraft had increased of late by over 50 percent and that Ukraine's infrastructure had come in for increased targeting.

Russia has not responded to these claims. 

(With input from Reuters)