Ukrainians near rebels’ stronghold

KIEV, Ukraine – The Ukrainian military is increasing pressure on the separatist stronghold of Donetsk, officials said Saturday, even as concern grows about deeper Russian involvement in the conflict.

The army had advanced to the edge of Horlivka, they said, which is a key shipping point for separatists about 25 miles to the northeast.

“We have approached Horlivka,” said Andriy Lysenko, spokesman for the National Security and Defense Council. “Donetsk will be next.”

The news comes as the U.S. accuses Russia of moving significant amounts of weaponry across the border, and building up forces on the Russian side of the frontier.

A fierce battle has been waged for weeks in Donetsk, particularly near the airport, which is a supply lifeline for much of the region, known as the Donbass. Those in the area report sounds of gunfire and shellings regularly. Lysenko said Saturday that the country aims to wage an urban war in Donetsk with few if any missile or air attacks.

The conflict there has already exacted a price, however, particularly in civilian casualties. On Thursday, Human Rights Watch released a report that said Grad rockets used by the Ukrainian army killed at least 16 civilians in Donetsk over the last two weeks.

The Ukrainian army has taken the cities of Lysychansk and Slovyansk to the north of Donetsk this month. The retaking of Slovyansk prompted President Petro Poroshenko to proclaim a turning point in the campaign.

Donetsk would be an even bigger win. The city of 1 million is at the epicenter of the pro-Russian insurgency. Although separatists would probably retreat to a few urban centers and continue to fight, most experts say that Ukrainian forces could triumph relatively quickly if Donetsk fell.

But Russia remains a wild card. The Pentagon says Moscow has been transferring more heavy weaponry to separatists; on Friday, a spokesman said the U.S. believed Russia was set to move up to a dozen 200-millimeter rocket launchers to separatists, some of the strongest weaponry it has supplied to date. Russia has also increased its troop count along the border to 12,000, the Pentagon said.

Deeper Russian involvement could make the conflict drag on, experts say.

U.S. officials also say Russia has launched artillery attacks across the border at Ukrainian forces in recent days. The Ukrainian government, meanwhile, has suggested that two fighter jets lost over eastern Ukraine this week may have been downed by missiles fired from Russian territory.

Russian President Vladimir Putin has denied supplying weapons to separatists or engaging in military activity along the Ukrainian border. The Russian Foreign Ministry on Friday called the recent U.S. intelligence reports of Russian military activity “an unrelenting campaign of slander.”