Tuesday's talks in Istanbul between Ukraine and Russia have concluded.

Russian delegation head Vladimir Medinsky told reporters the talks were "constructive."

Meanwhile, Alexander Chaly of the Ukrainian delegation told reporters that talks will continue, and in two weeks they plan to involve other countries in the negotiation process.

Ukrainian negotiator David Arakhamia said he believes enough has been covered to now involve the presidents of Ukraine and Russia in the talks.

Medinsky noted, "As a result of today's substantive conversation, we have approved and offer a solution, according to which a meeting between the heads of state is possible simultaneously with the initialing of the agreement."

"The proposed format is like this: first an agreement will be drafted, then the agreement will be approved by the negotiators and signed by the foreign ministers at a meeting, and then the possibility of a meeting between the heads of state will be discussed in order to sign this agreement," Medinsky said.

Ukrainian officials said a military alliance of other countries -- including the U.S. -- needs to be created to provide security protections to Ukraine.

U.S. Secretary of State Antony Blinken expressed skepticism about the talks, saying he would leave it to the Ukrainians to characterize any progress.

Russia's military will "drastically" decrease activity near Kyiv and Chernihiv to try to improve trust and aid further talks with Ukraine, Russian Deputy Defense Minister Col. Gen. Alexander Fomin said Tuesday.

"Due to the fact that the negotiations on elaborating a treaty on Ukraine's neutrality and nuclear-free status, as well as on providing Ukraine with security guarantees are shifting to the practical field, and taking into account the principles discussed during today's meeting," Fomin told reporters, "the Russian Defense Ministry has decided to decrease its military activity in the areas of Kyiv and Chernihiv drastically in order to increase mutual trust and create conditions required for further negotiations and for achieving the ultimate goal of reaching an agreement on and signing of the aforementioned treaty."

U.S. Secretary of State Antony Blinken was asked by reporters Tuesday about Russia's announcement that it will scale back operations around Kyiv and Chernihiv. He said it may be a "means by which Russia is, once again, trying to deflect and deceive people into thinking that it's not doing what it is doing, whether it's simply trying to regroup given the heavy losses that it's suffered -- I don't know." But any attempt to "subjugate" eastern or southern Ukraine will not succeed either, he added.

President Joe Biden will hold a call at 9:15am ET Tuesday with French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Mario Draghi and United Kingdom Prime Minister Boris Johnson to discuss the latest with Russia’s invasion of Ukraine, according to the White House.

Macron is also set to speak with Russian President Vladimir Putin on Tuesday.

-ABC News' Justin Ryan Gomez

More than 3.9 million people have been forced to flee Ukraine since Russian forces invaded on Feb. 24, according to the latest figures from the United Nations Refugee Agency.

The tally from the U.N. High Commissioner for Refugees (UNHCR) amounts to just over 8.8% of Ukraine's population -- which the World Bank counted at 44 million at the end of 2020 -- on the move across borders in 34 days.

More than half of the refugees crossed into neighboring Poland, UNHCR figures show.

-ABC News' Zoe Magee

About 631 residents of the bombed-out city of Mariupol in southeast Ukraine were able to evacuate on Thursday, according to a Ukrainian official.

Ukrainian Deputy Prime Minister Iryna Vereshchuk said the residents fled the city in private vehicles after 45 buses reserved to drive them out failed to make it into the city. Vereshchuk said another 600 civilians still in Mariupol plan to try to evacuate again on Friday.

Ukrainian President Volodymyr Zelenskyy said Thursday in an address to lawmakers of Australia, the Netherlands and Belgium that more than 90% of all buildings in Mariupol have been completely destroyed by Russian strikes.

"Thousands of peaceful Mariupol residents died, people are buried just in the city, in the courtyards of high-rise buildings, or rather, what is left of the high-rise buildings," Zelenskyy said.

-ABC News' Christine Theodorou