Pro-Russian rebels guard the road Tuesday near the village of Rossipne in the Donetsk region of eastern Ukraine, as Australian, Malaysian and Dutch investigators continue to examine the area of the downed Malaysia Airlines Flight 17.

The West has accused Russia of most likely providing the insurgents with surface-to-air missiles that may have been used to shoot down the Malaysia Airlines passenger jet over rebel-held territory July 17, killing all 298 people on board.

Also Tuesday, fighting in eastern Ukraine reached the main rebel stronghold of Donetsk as separatists and government troops exchanged rocket fire in neighborhoods on the edge of the city.

In a western district of Donetsk, rockets apparently fired from a government position landed in the courtyard of a one-story house, killing an elderly resident.

The spread of fighting into the city itself marks a decisive turn for the conflict, one that will arouse fears of an alarming escalation in the humanitarian crisis gripping the country’s easternmost regions.

As government troops try to tighten their encirclement of rebel citadels, officials in Kiev have warned of a spike in Russian troop numbers along the border, arousing renewed fears of intervention by Moscow.

— The Associated Press