Story highlights

NEW: Nine Ukrainian soldiers killed in clashes, Ukraine says

NEW: Twenty-seven soldiers also reportedly wounded

Three civilians were killed in overnight shelling in Donetsk

Kiev, Ukraine CNN  — 

Nine Ukrainian soldiers were killed by tank fire Monday at the airport in the flashpoint city of Donetsk, according to the Ukrainian National Security and Defense Council Information Center.

Twenty-seven were wounded in the fighting, said Andrey Lysenko, spokesman of the center, at his press briefing.

In a separate incident, three civilians were killed and five injured in shelling overnight in Donetsk, the website of the city office said Monday.

Residential and administrative buildings were damaged as a result of artillery fire, according to the site, which described the situation as tense.

Ukrainian government forces have been fighting pro-Russian separatists in eastern Ukraine for months.

Despite the ongoing violence in places such as Donetsk, Ukrainian President Petro Poroshenko insisted last week that a ceasefire signed with rebel leaders more than three weeks ago was holding.

Journalist Victoria Butenko reported from Kiev, CNN’s Lindsay Isaac reported from London, and CNN’s Jethro Mullen wrote from Hong Kong.