At least 26 people, including children, were killed during 24 hours of violence in eastern Ukraine as government forces stepped up their offensive against insurgents seeking their region's independence from Kiev, authorities said Tuesday.

The local government in Gorlovka city, in the Donetsk region, said that clashes between government troops and insurgents, which erupted on Monday, had killed at least 17 people, including three children.

In the neighboring town of Yasynovata, at least four people were killed and seven others wounded as the result of an air strike on an apartment building.

Heavy fighting and machine gun fire have been also reported in the Lugansk region. According to Lugansk city council's press service, at least five civilians were killed in a fierce battle for control of the city over the past 24 hours.

Local media reports suggested that a team of international investigators were again prevented from reaching Malaysia Airlines Flight MH17's crash site, which lies not far from the epicenter of the bloody conflict. However, there was no official confirmation of the report from authorities.

Ukrainian forces have been fighting with insurgents since mid-April to regain control over the seized cities and towns in eastern part of the country.

According to the United Nations, the death toll in the clashes has reached at least 1,129 people, while around 3,442 others were wounded.

Ukraine said it had lost 325 of its troops and 27 border guards in the conflict.