The United Nations has said that at least 117,000 people have fled their homes and are currently displaced due to the conflict in eastern Ukraine.
According to the United Nations agency for refugees (UNHCR), local Ukrainian authorities have so far registered some 117,000 people flooding out of the east to other regions of the country.
The UN agency estimates that about 730,000 Ukrainians have left the country for Russia this year.
"According to the Russian authorities, and we believe that number is credible, there are about 730,000 Ukrainians who have crossed into Russia since the beginning of the year," Vincent Cochetel, head of the UNHCR's European Bureau, told reporters in Geneva.
UNHCR warned that intensified battles could lead to a "massive exodus".
In addition, around 168,000 Ukrainians had as of August 1 applied to Russian authorities for asylum, refugee and other kinds of protective statuses such as temporary residence permits, he said.
"We don't call all of those people refugees," he said, adding that only some of the 168,000 who had applied for protective status fell into that category.
But according to Russian authorities, more than half a million more Ukrainians have gone to Russia since January under the country's visa-free regime, without registering, Cochetel said.
The UNHCR said 87 percent of those displaced inside Ukraine had fled the main rebel strongholds of Donetsk and Luhansk, while the remainder were from Crimea, which was annexed by Moscow in March.
The already staggering numbers of displaced people were rising fast, Cochetel warned, saying that over the past two weeks, 1,200 people had been flooding out of Donetsk and Luhansk into other parts of Ukraine each day.
"Those people are leaving with very little," he said. "Some of them arrive with almost no belongings or got some of their belongings confiscated at checkpoints."
With the Ukrainian army closing in on Donetsk, there is fear that intense fighting could move into the city centre, which is home to at least one million.
"Fighting in highly densified urban areas could lead to a massive exodus and massive destruction," Cochetel said, warning that water shortages in Luhansk could also spark more people to leave.