KYIV, UKRAINE -- Russia attacked the Ukrainian port city of Izmail for the fourth time in five days, Ukrainian officials said Thursday, in what has become a sustained campaign to target Ukraine's ability to export grain.

The Danube River port area was attacked with Shahed drones aiming at civilian and port infrastructure, the governor of the Odessa region, Oleh Kiper said. A truck driver was wounded and grain silos were damaged, he said.

Ukrainian war crimes prosecutors inspected the wreckage at the scene close to port infrastructure on Thursday, according to a statement from the Ukrainian Prosecutor's Office.

The Ukrainian military said it shot down 25 out of 33 drones launched by Russia overnight, most of them at the Odessa region, Ukraine's agriculture export hub, as well as the northern Sumy region, the military said.

Russia has escalated attacks on Ukraine's grain export infrastructure since mid-July, when it exited a U.N.-backed deal that had allowed for the safe shipping of Ukrainian grain during the war.

 In Russia, five drones were shot down from over three regions overnight, including one attempting to strike Moscow, officials said. There were reports of no casualties.

The attack in Izmail came one day after a Russian missile struck a busy market in the eastern Ukrainian city of Kostiantynivka in Donetsk, killing 17 and wounding at least 32.

The attack overshadowed a two-day visit by U.S. Secretary of State Antony Blinken, aimed at assessing Ukraine's 3-month-old counteroffensive and signalling continued U.S. support for the fight.

While touring northern Ukraine on Thursday, Blinken said the death and destruction in Kostiantynivka was "what Ukrainians are living with everyday."

Blinken visited a school in the village of Yahidne where hundreds of residents were imprisoned when Russian forces occupied the village at the start of the full-scale invasion.Blinken said Russian atrocities continue. "Just yesterday, we saw the bombing of a market, 17 people or more killed," he said. "For what?"

Earlier, Blinken visited a Kyiv region facility of the State Border Guards of Ukraine and went to see a demining team working to clear unexploded ordnance from a 45,000 square meter site that included a farm.

Blinken announced $90.5 million in demining assistance as part of a package of U.S. military and humanitarian aid totalling over $1 billion on Wednesday.

While Ukraine's ports have come under attack, drone attacks on Crimea, which Russia annexed from Ukraine in 2013, and in Russia itself also have become increasingly common in recent months. In recent weeks, drones have repeatedly targeted Moscow, with some hitting buildings in the city center, while others being shot down on the outskirts of the city.

Russia's Defence Ministry blamed the overnight attacks in Russia on Ukraine, which does not take credit for strikes inside Russia. One drone targeted Moscow, but was shot down southeast of the city without causing any damage or injuries, Mayor Sergei Sobyanin said.

Two more drones were shot down over the southern region of Rostov, which borders Ukraine, said regional Governor Vasily Golubev. The debris fell in the center of Rostov-on-Don, the region's capital, damaging several cars and shattering windows in three buildings, Golubev said. One person sought medical assistance.

Two other drones were shot down over the Bryansk region, which also borders Ukraine, Governor Alexander Bogomaz reported. Drone debris damaged a railway station and several cars, he said.