SHAKHTARSK, Ukraine — Heavy fighting raged today around the Malaysia Airlines crash debris field, preventing an international police team charged with securing the site from even getting there.

Government troops have stepped up their push to win back territory from pro-Russian separatists in fighting that the United Nations said has killed more than 1,100 people in four months.

The international delegation of Australian and Dutch police and forensic experts stopped today in Shakhtarsk, a town around 20 miles from the fields where the Boeing 777 was brought down.

The police team is to secure the rebel-controlled area so that investigations can begin.