Charles McPhedran and Anna Arutunyan

Special for USA TODAY

KIEV, Ukraine — Ukrainians in this nation's capital prepared themselves for war after results from the disputed referendum in the Crimea showed an overwhelming majority in favor of joining the Russian Federation.

Crimea's election committee said that 97% of voters backed a union between the largely ethnic-Russian peninsula and the huge neighboring country.

"I have a feeling that today is the last calm day," said Lubna Petrova, a grandmother who was watching TV coverage of events in Crimea. "Tomorrow Putin will start a war against the Ukrainian nation, and he won't stop until he takes over the entire country."

In Simferopol, the mood among Russians was festive after polling stations closed at 8 p.m., with a concert held in the city's center square. Thousands turned up brandishing flags and dancing to live pop music.

Residents of Crimea, up to 60% percent of whom are Russian, were given a choice of either joining Russia or opting for more autonomy from Ukraine under the 1992 constitution. The status quo, in which Crimea is a semi-autonomous region of Ukraine, was not an option.

Crimea's Prime Minister Sergey Aksyonov, who was installed during the pro-Russian armed occupation of the peninsula, announced via Twitter that he planned make a formal request to join the Russia Federation on Monday.

Russia's pro-Kremlin parliament welcomed the referendum and pledged to facilitate Crimea joining Russia. Russian President Vladimir Putin, who authorized sending Russian troops to Ukraine on March 1, has insisted that Russia is only protecting Russians in Ukraine and would deploy armed forces only if necessary.

Putin told German Chancellor Angela Merkel in a Satuday phone call that Crimean residents were voting in accordance with international law, in particular with Article 1 of the United Nations Charter, stipulating the right of people to self-determination, according to an official Kremlin statement.

Meanwhile, tensions continued to mount in southern and eastern Ukraine's as a large pro-Russian rally filed through the streets of Donetsk in the industrial Donbass region before storming a prosecutor's office, videos released by pro-Russian activists showed. Several people have died in Donetsk and Kharkiv, a large city in east Ukraine, as pro-Ukrainians and pro-Russian supported have clashed in recent days.

Putin has expressed concern about the violence in southern and eastern regions of the country, although the U.S. State Department attributes it to Russian interference. Many fear that Moscow could be orchestrating violence as a pretext to invading those regions of Ukraine.

"These are two nations whose history are intertwined throughout history," said Keir Giles, associate fellow in the International Security and Russia and Eurasia Programme at Chatham House, an independent policy institute. "The instability in Ukraine following the removal of President Yanukovych provided president Putin with an ideal chance to move briskly and efficiently to take control of a key region while the interim Ukrainian government was inert."

In the Ukrainian capital's Independence Square, the focus of months of protests that toppled Russian-backed President Viktor Yanukovych, military preparations for a conflict with Russia were in full swing even ahead of the referendum's outcome.

Many men and boys on the square were dressed in combat fatigues sporting military insignias. A number of shops surrounding the square were hosting paramilitary units or the Ukrainian government's new national guard. All were signing up as volunteers to serve on the front in the event of a Russian attack.

"We need to be ready in case that something happens," said Stanislav Stoqnov, who was lining up to join the government's guard. "I would like to serve in Kiev."

One paramilitary commander told USA TODAY that he was preparing for the possibility of a Russian attack in east Ukraine following the referendum on Sunday night.

"The people are showing willingness to fight. But the government doesn't seem to be doing what it should," brigade commander Rodak Sashawitzer, of far-right Pravy Sektor, said outside a store where his unit is housed. "We need to prepare the civil population for the chaos that will follow a war breaking out."

Russian state television had warned that pro-Russian defense forces, which had flooded the Crimean peninsula since the beginning of the month, were on high alert to prevent "provocations" from pro-Ukrainian forces during the vote. However, not a single armed guard was seen in the vicinity of Polling Station No. 08086, at a Crimean gymnasium on Simferopol's Kiev Street.

"Of course I voted for joining Russia, I was born in Russia," said Raisa Dragunova, a pensioner in her 70s who voted at the gymnasium, tearing up as she spoke. "The referendum wasn't a surprise at all. I was so happy."

Many of the minority Crimean Tartar Muslim community boycotted the poll, but even so, Russian media reported a huge turnout.

"I'm for Russia. To be honest, I've waited for this for 20 years," said Eduard Kutalitov, 38, a Russian factory worker. "I am a native of Simferopol, and I identify with Russia."

Kutalitov said he believed that troops were sent to maintain law and order, but he hasn't seen any disorder from pro-Ukrainian forces. "It's quiet here, there's not going to be any war."

Some who opposed Crimea joining Russia did not vote because they said the referendum didn't give them any option.

"There's no choice to vote against joining the KGB-run government," said Nikolay Vasilyevich, a Ukrainian professor in Simferopol. "How can you vote with Russian troops around? Crimea will never join Russia, it will lead to war."

Mikhail Malyshev, head of the referendum's organizing commission, told news agencies there were no voting irregularities. But local media reported instances of voter fraud.

There were also reports of pressure on voters and journalists. Tatyana Tkachenko, a native-Russian freelance reporter from Cyprus, was held at gunpoint and arrested after a local defense squad stormed the apartment of a pro-Ukrainian activist she was interviewing in Sevastopol.

"I was thrown to the floor and they held a gun to my temple. It was very cold," she told USA TODAY. "They questioned me until 4 in the morning and threatened to jail me for espionage. Then they let me go without any explanation."

Arutunyan reported from Simferopol, Ukraine. McPhedran reported from Kiev. Contributing: Luigi Serenelli from Berlin, Associated Press