KYIV, July 6 - Ukraine has so far staved off any major Russian advance into the north of its Donetsk region, but pressure is intensifying with heavy shelling on the city of Sloviansk and nearby populated areas, the Ukrainian military said on Wednesday.

After capturing the city of Lysychansk over the weekend, Russian forces are turning their sights to parts of the Donetsk region that remain under Ukrainian control, including the cities of Slovyansk and Bakhmut, The Wall Street Journal reported.

The General Staff of Ukraine’s Armed Forces said Russian troops were seeking to strengthen their tactical positions on the Slovyansk front, firing on the area near the towns of Krasnopillya and Bohorodychne using mortars, rockets and other artillery.

Russian forces are now effectively in full control of the Luhansk region. Donetsk and Luhansk together form the heavily industrial Donbas region, where Russia has concentrated its firepower since retreating from around the capital Kyiv in March.

Russia fomented a rebellion in Donbas in 2014, carving out two Kremlin-run statelets in parts of the region, after annexing Crimea from Ukraine the same year. Russia is now seeking to take full control of Donbas.

Western countries are steadily increasing their military support for Ukraine’s armed forces, sending more advanced artillery systems, among other weapons. But Ukraine’s government has pressed the U.S. and its European allies in the North Atlantic Treaty Organization to send more weapons faster, to help its defenders to cope with Russia’s advantage in firepower and ammunition.

Russian troops have made slow but steady territorial gains in eastern Ukraine in recent weeks, relying on intensive artillery bombardments of Ukrainian troops’ positions. The Ukrainian defenders have sought to inflict losses on Russian forces before withdrawing to deeper defensive lines in the region.

Both sides are widely believed to have suffered heavy casualties in the battle for Donbas, which has become one of the bloodiest battles between two states in Europe since World War II.

Serhiy Haidai, the governor of the Luhansk region, said Ukrainian troops were holding Russian forces back at the border between Luhansk and Donetsk, and had thwarted Russia’s efforts to cut off the highway between the cities of Lysychansk and Bakhmut. “Under the pressure of our defenders, the enemy was forced to retreat,” Haidai said.

Russian shelling has killed at least five civilians in the Donetsk region since Tuesday, including one in Slovyansk and two in Avdiivka, said Pavlo Kyrylenko, the head of the region’s military administration.

The arrival in June of U.S. High Mobility Artillery Rocket Systems, or Himars, has strengthened Ukrainian troops’ hand by enabling them to target Russian weapons and ammunition depots far behind the front line. In an interview, Oleksiy Danilov, secretary of Ukraine’s National Security and Defense Council, said nine mobile Himars and similar rocket-launch systems donated by the U.S. and its allies are now operating inside Ukraine.

NATO countries are also seeking to boost Ukraine’s military capability through training. U.K. Defense Secretary Ben Wallace said the first rotation of Ukrainian soldiers had recently arrived in Britain, where they will undertake courses for several weeks including weapons training, battlefield first aid, patrol tactics and training on the law of armed conflict.

President Volodymyr Zelensky said in his nightly address on Tuesday that his government was seeking to procure modern antimissile systems to protect cities and towns behind the front line that have been frequently targeted by Russia.

This is a maximum task for our state—to provide basic security for Ukrainians,” Zelensky said. “But the fulfillment of this task depends not only on us, but also on the understanding of our fundamental needs by our partners.” (wsj/ez)