Ukraine is stepping up its long-distance attacks into Russian-occupied Crimea and the Black Sea, launching several new strikes Thursday, in a campaign to break down the Kremlin’s war effort by hitting targets far behind the front lines where soldiers are fighting and dying.

The Ukrainian military said it had hit a Russian surface-to-air missile defense system in Crimea and two Russian vessels at sea, a day after it struck two Russian warships docked in Crimea. The statements could not immediately be confirmed or refuted. The Russian Defense Ministry said only that attacks on a ship in the Black Sea had failed.

In recent weeks, Ukraine has sharply accelerated the pace of strikes in and around the Crimean Peninsula, a critical hub for the Russian military where it stockpiles troops, fuel, ammunition and other supplies and funnels them to the battlefields in southern Ukraine. The peninsula also contains the primary base, at Sevastopol, of the Russian Black Sea Fleet that is blockading Ukrainian ports.

The fight to reverse the Russian invasion stretches across multiple regions and hundreds of miles, but the Ukrainian military has long maintained that it cannot be won without taking aim at Russian assets and operations in Crimea. And since Moscow ended a grain-shipping agreement in July, Ukraine has been trying to establish a somewhat safe corridor for civilian freighters, in part by degrading the Russian fleet and forcing it to keep a wary distance.

“The way to victory on the battlefield is to defeat the logistics of the Russians,” Andriy Yermak, a senior adviser to Ukrainian President Volodymyr Zelenskyy, said in a statement after the Crimea strikes Wednesday. Defeating Russia, he said, depends on not giving Moscow “the opportunity to preserve the military potential for waging an aggressive war.”

On another front, the United States on Thursday announced economic sanctions against about 170 individuals and companies, most of them Russian, whom it described as contributing to the Kremlin’s war effort through industry, finance, technology or energy, adding to the thousands already under sanctions.

Ukraine’s 3-month-old counteroffensive has made only grueling, slow-moving progress at the expense of casualties and equipment.

Ukraine’s military said Thursday that it had hit an S-400 Triumf surface-to-air missile battery, one of Russia’s most sophisticated air defense systems, near Yevpatoriya, in western Crimea. The Russian Defense Ministry did not comment on the claim.

The attack featured both aerial drones and missiles, according to a Ukrainian security official who spoke on the condition of anonymity to discuss operational details. First the drones disabled Russian radar antennas, the official said, so they would not detect what came next: Neptune missiles that hit the S-400 battery.