Ukraine's army on Wednesday accused pro-Russian forces of launching a big new attack against government positions in breach of a shaky ceasefire.
Rebel forces began a "large-scale offensive against Ukrainian positions" close to the separatist stronghold of Donetsk at 4 a.m. local time using about a dozen tanks and up to a thousand troops, Ukraine's General Staff said in statement.
It added that government troops had fought back against the attack using heavy artillery.
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Senior rebel commander Eduard Basurin said that one civilian was killed in Donetsk and four were wounded as a result of fresh fighting.
Separately Volodymyr Kolesnyk, from the Donetsk region's health department loyal to Kiev, said that six civilians had been wounded in Mariinka, a settlement just to the west of Donetsk.
He added that "more than 11" Ukrainian soldiers had been wounded as well.
Basurin confirmed that fresh fighting was under way around the settlement of Mariinka but denied that rebel forces had taken control of it.
Earlier in the day, Ukrainian authorities accused the pro-Russian rebels of attacking its troop positions near Mariinka, using Grad rockets and tanks.
Mariinka and Georgiivka, areas under control of Ukrainian forces about 19 miles from Donetsk, were under "intense shooting" since the morning, Vyacheslav Abroskin, chief of the Donetsk region's police, loyal to Kiev, said.
"The enemy is shooting on Mariinka using Grad (rockets) as well as tanks," he said, adding that there were victims but without giving figures.
He added that the checkpoints at Georgiivka and Kurakhove, about 40 kilometres from Donetsk, were closed to traffic owing to the shooting.
Ukrainian military spokesman Leonid Matyukhin confirmed that the Kurakhove checkpoint was closed Wednesday.
Fighting has intensified recently around key hotspots on the frontline in eastern Ukraine despite a fragile truce brokered by the West in February.
The conflict between the Ukrainian army and insurgent forces has killed more than 6,400 people since April 2014. Kiev and the West accuse the Kremlin of supporting and arming the pro-Russian separatists, which Moscow denies.