Russian shelling pounded eastern and southern Ukraine as President Vladimir Putin said Moscow would only ease the path for Black Sea exports of Ukrainian grain if the West lifts sanctions on Russia's shipments.
Russian strikes hit the eastern city of Kramatorsk on Tuesday, killing one person, local authorities said.
AFP journalists said a four-story residential building had been hit in the city in the Donbas region. One man with a bloodied head lay on the ground, before being taken away by the emergency services.
"He was just walking by and was hit," said one woman, who declined to give her name, visibly shaken after the bombardment.
Russia's invasion of Ukraine in February has killed thousands and displaced millions, but also hampered shipments from one of the world's biggest exporters of wheat and other grain, sparking fears of global food shortages.
Putin, in Tehran for talks with his Turkish counterpart Recep Tayyip Erdogan, on Tuesday said "progress" had been made in discussions towards exporting grain from Ukraine.
After talks with both Erdogan and Iran's president, Putin told reporters that any deal hinged on the West's willingness to yield some ground.
"We will facilitate the export of Ukrainian grain, but we are proceeding from the fact that all restrictions related to possible deliveries for the export of Russian grain will be lifted," he said.
NATO member Turkey has been using its good relations with both the Kremlin and Kyiv to try and broker an agreement on a safe way to deliver the grain.
'Victory before winter'
On Wednesday, Russian and Ukrainian delegations are due to meet in Istanbul alongside Turkish and UN representatives, with hopes rising for an announced accord.
The EU's foreign policy chief Josep Borrell warned this week that the grain impasse was "an issue of life and death for many human beings".
And a document consulted by AFP Tuesday showed that the European Commission is proposing to unblock assets at Russian banks linked to trade in food and fertilizer.
Along the Black Sea coast, Kyiv said that a barrage of seven cruise missiles had wounded at least six people, including a child, in the southern coastal region of Odessa.
The Russian defense ministry claimed that strikes on Odessa had destroyed a stockpile of Western-supplied weapons.
Russian Defense Minister Sergei Shoigu ordered troops earlier this week to prioritize the destruction of long-range artillery supplied by the United States and Ukraine's other Western allies.
Observers credit the weapons with altering battlefield dynamics, giving Ukraine the capacity to hit Russian arms depots and command posts deep inside territory controlled by Moscow.
Ukrainian Defense Minister Oleksiy Reznikov, during a visit to the United States, urged the West to drastically step up its supply of precision rocket systems, calling them a "game-changer".
In Washington, National Security Council spokesman John Kirby said the United States believes that Russia is moving ahead with plans to annex more Ukrainian territory.
"Russia is beginning to roll out a version of what you could call an annexation playbook, very similar to the one we saw in 2014," when it invaded and annexed Crimea, Kirby said.
Zelensky's chief of staff Andriy Yermak underlined in an interview published Tuesday that Ukraine had to win its war with Russia before winter, telling Ukrainian weekly Novoye Vremya that if Moscow has time to regroup, it will be "more difficult".
On the diplomatic front, Russia's close ally Syria announced Wednesday it was severing ties with Ukraine, according to an unidentified foreign ministry official, cited by state news agency SANA.
Kyiv had already announced it was cutting ties with Syria late last month, after Damascus recognized the Russian-backed breakaway republics of Donetsk and Lugansk in eastern Ukraine.
Ukrainian lawmakers on Tuesday endorsed the president's decision to sack the country's top prosecutor and security chief, backing Ukraine's largest political shake-up since Russia invaded.
Several Ukrainian deputies said lawmakers at the parliamentary session in Kyiv had overwhelmingly backed President Volodymyr Zelensky's shock call to remove the senior officials.
"Parliament voted to dismiss Iryna Venediktova as prosecutor general," said David Arakhamia, a lawmaker affiliated with Zelensky.
Other deputies said the plea to remove security chief Ivan Bakanov had secured the required 226 votes.
Zelensky late Sunday said he was suspending the senior law enforcement officials -- and that 650 cases of suspected treason were under investigation.
He replaced Bakanov on Monday and described the shake-up in the security services as an "audit", saying 28 security officials were facing dismissal.
The governor of Mykolaiv, a southern region under constant Russian rocket fire, meanwhile on Tuesday promised a $100 reward for anyone who could help to identify people who have been collaborating with Russia by providing it with the locations of Ukrainian troops or coordinates of potential targets.