Ukrainian President Volodymyr Zelensky on Sunday announced the departure of defence minister Oleksiy Reznikov, calling for "new approaches" a year and a half into Russia's invasion.
The announcement came hours after Ukraine fought off an attack by Russian drones in the southern Odesa region Sunday that hit a Danube port on the border with NATO member Romania.
"Oleksiy Reznikov has been through more than 550 days of full-scale war," Zelensky said in his daily evening address.
"I believe that the ministry needs new approaches and other formats of interaction with both the military and society at large."
He nominated Rustem Umerov, a Crimean Tatar who has been head of the State Property Fund since last year, to replace Reznikov -- subject to approval by Ukraine's parliament.
News of Reznikov's removal comes with Kyiv's counteroffensive underway and Ukraine's general push against corruption in response to EU requests.
- Russian drone attacks -
Russia, meanwhile, continued its military campaign against Ukraine's infrastructure.
Moscow has launched attacks on targets in the Black Sea and the Danube river for weeks now, since pulling out of a key deal that allowed the safe passage of ships carrying grain.
This latest attack came on the eve of a summit in Russia between President Vladimir Putin and Turkish leader Recep Tayyip Erdogan, who hopes to revive the grain deal.
Ukraine said Russia had hit the Odesa region with a barrage of Iranian-made Shahed drones.
But Kyiv also said that some of the drones hit the Danube area, wounding at least two people in attacks on "civilian industrial" infrastructure.
Russia's army said it had targeted "fuel storage" facilities in the Ukrainian port of Reni, which lies on the Danube river that separates Ukraine from Romania.
Moscow has targeted Reni and the Danube port of Ismail -- both near Romania and across the war-torn country from fighting hotspots -- several times over the last few weeks.
Reni, which also lies close to Moldova, is both a sea and river port, and important transport hub.
Bucharest's defence ministry condemned the attacks as "in deep contradiction with the rules of international humanitarian law". But it stressed that the attacks had not posed any direct threat to Romanian territory.
President Maia Sandu of neighbouring Moldova also denounced the "brutal" attack.
- Ukrainian breakthrough in south -
The Odesa region attacks came as Kyiv has claimed some successes in its counter-offensive on the southern front this week.
On Wednesday, Kyiv said it had recaptured the village of Robotyne, calling it a strategic victory that would pave the way for its forces to push deeper into Russian positions towards Moscow-annexed Crimea.
General Oleksandr Tarnavskiy, leading the southern counteroffensive, told The Guardian newspaper this weekend that Kyiv's army has made an important breakthrough by breaching Russian lines near Zaporizhzhia.
"We are now between the first and second defensive lines," Tarnavskiy -- who led Ukrainian troops to liberate the southern city of Kherson -- told the UK paper.
Heavily mined territory had slowed Ukrainian troops, he added, saying sappers had cleared a route by foot and at night.
The paper quoted him as saying that Kyiv's forces were now back on vehicles and that Russia had redeployed troops to the area.
"But sooner or later, the Russians will run out of all the best soldiers," Tarnavskiy said.
"Everything is ahead of us."
At the same time he admitted difficult losses, saying that "we are losing the strongest and best."
- Moscow's recruitment drive -
Russia has not announced another mobilisation, seen as an unpopular measure, but has led an active campaign to attract more men into the military as its Ukraine offensive drives on into a 19th month.
Ex-president and Security Council chairman Dmitry Medvedev said Sunday that Moscow had recruited 280,000 people into the army since the start of the year, TASS news agency reported.
"Part of them were in the reserves, part of them volunteers and other categories," he said during a visit to the Far Eastern Russian island of Sakhalin.
In August, Medvedev said the army had recruited around 230,000 people since the start of the year.
AFP is not able to independently verify these numbers.
In September last year, the Kremlin made a U-turn on promises not to announce a military draft, announcing a partial call-up to make up for losses on the Ukrainian front that led to the recruitment of 300,000 men.
But the announcement also triggered another wave of emigration from Russia, with hundreds of thousands believed to have fled abroad.