NAIROBI, Kenya — African citizens remained stranded across Ukraine on Friday, even as their governments called for an immediate cease-fire, urging Russia to respect the territorial integrity of Ukraine and to withdraw its troops.The rapidly escalating conflict is trapping thousands of African nationals in multiple cities, many of them medicine and science students at Ukrainian universities. As Russia began shelling Ukrainian towns and cities on Thursday, many of the students took to social media to share their fears and frustrations and plead for help from their governments.“We are really terrified,” Mohamed Abdi Gutale, a Somali citizen who is a first-year medicine student at Kyiv Medical University, said in a telephone interview on Friday morning.Just hours before, Mr. Gutale said, he and 168 other Somali nationals were able to secure buses to transport them from Kyiv, the capital, to Lviv in western Ukraine. He said they didn’t know what their next plans were, “but we will decide what to do once we get there.”Russia has staunch allies across Africa, with Russian mercenaries battling insurgents in Mali, its companies mining for diamonds in the Central African Republic and its weapons finding ready customers in Egypt and Burkina Faso. In 2019, Russia convened a summit of African leaders in the southwestern Russian city of Sochi as part of its ambition to revive its economic, political and military influence in the continent.But no African nation has come out to support the invasion of Ukraine, and some have expressed their dismay at the Russian attack.On Thursday, the chairman of the African Union Commission, Moussa Faki Mahamat, and President Macky Sall of Senegal called on Russia “and any other regional or international actor to imperatively respect international law, the territorial integrity and national sovereignty of Ukraine.”South Africa, which is part of the group of five emerging economic powers known as BRICS — Brazil, Russia, India, China and South Africa — also urged Moscow to withdraw its forces from Ukraine.“Armed conflict will no doubt result in human suffering and destruction, the effects of which will not only affect Ukraine but also reverberate across the world,” South Africa’s Department of International Relations and Cooperation said in a statement. “No country is immune to the effects of this conflict.”In the lead-up to Russian invasion this week, Gabon, Ghana and Kenya, which are current nonpermanent members of the United Nations Security Council, also expressed their concerns and denounced the dangers of using force to change borders.“The conflict will cause reputational damage to Russia,” said Murithi Mutiga, the Africa program director at the International Crisis Group. “Many on the African continent cheered Moscow’s vocal opposition to American-led wars in Iraq and Libya and now Russia will come across as the aggressor in a war of choice against a less powerful neighbor.”As the crisis unfolded this week, however, one African leader headed to Russia. Lt. Gen. Mohamed Hamdan, Sudan’s second most powerful man, on Thursday met with Russia’s foreign minister, Sergey V. Lavrov, as part of a trip aimed at improving diplomatic and economic ties. General Hamdan, also known as Hemeti, was among the generals who carried out a coup in October that derailed Sudan’s democratic aspirations.As the war began on Thursday, African governments scrambled to respond to citizens’ pleas for evacuation. Abdisaid M. Ali, Somalia’s foreign minister, said in an interview that his office had contacted countries such as Poland in an effort to provide legal entry to about 300 Somalis. Francisca K. Omayuli, a spokeswoman for Nigeria’s Ministry of Foreign Affairs, said in a statement that it would evacuate its citizens once airports were reopened.