Hundreds of thousands more have fled Ukraine, many crossing the border into Poland.
Foster, 34, from Mount Maunganui, said his fiancee, Anna Kaplina, her two children, her parents and her brother, who was part of the civilian militia, all lived in the city of Poltava.
Poltava is a city of about 285,000 people on the Vorskla River in central Ukraine.
"Anna is from a large extended family in Ukraine, and half of her family lives in Russia.
Foster said his 35-year-old fiancee was a professor of economics and trade and owned a digital marketing company.
Michael Foster and Ukrainian fiancee Anna Kaplina are set to reunite on March 21. Photo / Supplied
He said he had tried to arrange a flight for Kaplina and her children stuck in war-torn Ukraine since the invasion to escape to Hungary's capital Budapest so he could join.
However, he said that was not possible because Hungary closed its airspace like some other European Union countries, and airlines had cancelled flights into Ukraine.
Foster earlier said it was "devastating news" when Kaplina told him about the invasion, as he had tickets to join her in April after being separated for two years because of Covid.
They had even talked about possibly getting married during the visit, he said.
"Unfortunately, her father is remaining steadfast in his decision that he won't leave his little farm in Poltava, and Anna's mother won't leave without him."
Foster said Kaplina and her children were now due to leave Poltava on a train last night heading to Chelm city in Poland, about 25km from the Ukrainian border.
"It's about a 12-hour trip but it depends on whether the trains are running on time and they may have to wait a while along the way to get the connecting train to Chelm.
"Anna hopes friends can pick them up from the train station and a friend was helping her find a safe place to stay so they won't be stuck out in the cold," he said.
"I leave Auckland about 6pm on March 20 and I'm flying to Warsaw via Kuala Lumpur and Dubai and will arrive in Warsaw on March 21."
Foster said the Emirates flights would take him about 30 hours and Kaplina would arrange to meet him in Warsaw where they would discuss their next moves.
"I've got a 90-day visitor's visa so it gives us a little bit of time but what happens next is still very much up in the air."
He said it was a "huge relief" to know that Anna was going to be out of war-torn Ukraine and he could soon join her and the children.
"Once I get there we can sit down and discuss our future plans, and possibly we will head to the UK. But it's still too early to know what the best thing is for us to do next."
Foster said his employer and manager were both "very supportive" of his decision and had told him if he decided to come back to Tauranga the job would still be open to him
"They're treating my trip to Poland like a bit of an extended holiday break, and so grateful to them both for that."
He said Kaplina was naturally upset to leave her parents, her brother and her cat behind but her father refuses to leave his little farm and her mother is staying with him.
Foster said it has been a "pretty hard and stressful" time and had not slept much.
"March 20 cannot come soon enough. I'm really hoping I stay well and don't get Covid-like symptoms so the airline won't let me fly ... That would just be devastating.
"All I want to do is get to Anna and the children so I know they're safe."
