Russia is using a display of force combined with intense psychological pressure in an attempt to disarm Ukrainian military units in Crimea, according to accounts of several confrontations relayed to the Guardian.

On a day of confusion and rumours, Russian troops without insignia were still surrounding almost every Ukrainian military installation in Crimea, and an unsuccessful attempt was made to entice naval officers to defect to the Russian side.

In one tense confrontation, one of Russia's most senior army officers told a group of angry Ukrainian marines that he was carrying out Vladimir Putin's instructions to disarm Ukrainian forces. Igor Nikolayevich Turchinyuk told the marines at Feodosia that he wanted them to lock their weapons in a warehouse and surrender to Russian guards, according to an audiotape of the encounter obtained by the Guardian.

Turchinyuk identified himself on the tape as the deputy commander of Russia's entire Southern Military Region, which includes Russia's Black Sea fleet based in the Crimean port of Sevastopol, leased from Ukraine

One marine asks: "Am I a terrorist? Are we causing a threat to the Black Sea fleet of Russia?" Turchinyuk replies: "We have an order, which we are carrying out. The goal of me coming here … is to carry out the task given by the president of the Russian Federation in agreement with your legitimately elected president [Viktor Yanukovych]."

The statement that Russian troops are in Crimea at Yanukovych's request was made in public late on Monday at a session of the UN Security Council. Russia's ambassador to the UN said Yanukovych had made the request to Vladimir Putin on Saturday, even though in his only public appearance since fleeing to Russia, Yanukovych said he thought Russian military intervention was unnecessary.

During another encounter at the headquarters of Ukraine's fleet on Monday morning, Ukrainian navy officers rejected pleas for them to defect to the self-declared Crimean government.

The naval head, Denis Berezovsky, who on Sunday announced he was defecting to the Russian-backed Crimean authorities, addressed officers at naval command in Sevastopol to try to convince them to follow suit. But his replacement, Serhiy Haiduk, was also present and appeared to win the day.

The officers broke into applause as Haiduk read them an order from Kiev removing Berezovsky from his position, and told them that Berezovsky was facing treason charges. When Haiduk had finished his dry but compelling address, the officers spontaneously broke into the national anthem, and some were seen to cry. Berezovsky showed no visible sign of emotion.

"I know my men will stay loyal to their oaths," Haiduk told the Guardian before the address. "What Berezovsky has done is a matter for him alone. When he brought intruders in here, we did not offer armed resistance as would have been our right, in order to avoid any provocations the other side would like."

Officers at the HQ said Berezovsky had been guilty of treachery twice, the first time when he broke his oath, and the second time on Monday morning, when he requested permission to enter the headquarters and let several Russian special forces officers slip in behind him.

When Berezovsky requested questions from the officers, a chorus of criticism broke from the ranks. "In what way exactly did foreign powers intervene in Kiev, compared to the way they are intervening now in Crimea?" asked an officer to applause. "Don't ask provocative questions," Berezovsky barked back.

"We are resolving the matter by peaceful means, but we will never surrender our weapons," Haiduk said.

Berezovsky refused to comment to the press. In the end, he left the building accompanied only by his guards.

While the navy was asked to defect to Crimean authorities, those at bases in Kerch and Bakhchisarai said they had been asked by the Russians not only to defect to Crimean authorities but to the Russian army itself.

At Bakhchisarai, Lieutenant Colonel Vladimir Dokuchayev said: "There were suggestions that we joined the 'Crimean people', whatever that means, but first and foremost they asked us to join the Russian army. There was no talk of how this would work logistically, it didn't get to that. We said no, obviously."

There is tremendous pressure on the troops, surrounded as they are by Russians, and many of them have their own domestic pressure. Many ethnic Russians in Crimea favour the idea of a union with Russia, and some of them are sending messages to friends and relatives in the army urging them to desert.

"Many of us are receiving messages and calls from friends and family," said Dokuchayev. "Of course, that is never going to work for officers, it's pointless, but it has worked on some of the rank and file. We don't obstruct them, if people want to leave, they can."

He admitted that some had taken up the offer, but would not say how many, except to claim it was "a small number". A Ukrainian television journalist present at Bakhchisarai begged an interior ministry representative to ask authorities in Kiev to make more public statements in support of the troops in Crimea.

"We've had a lot of people calling in, they are terrified, they want to keep their oath but they don't know what is happening and are worried about getting proper support from Kiev," he said.

Among the officer class, however, even those who are fans of Russia are refusing to budge. One voice on the tape from Feodosia says: "From my childhood I have lived right next to Russia, we have always looked at Russia like an older brother or a helper, and we always were thrilled by your courage in different wars and operations, and saw you as a defender and expected help in any situation. Nobody could have imagined that such an awful time would have come to our country, but in our weakest moment, you have decided to do this. Do you not think your current behaviour will ruin not only our country but yours?"

The general responds with a long answer about Russia's greatness, which culminates in an ode to the Winter Olympics, held last month in Sochi. "The international community trusted Russia to hold the Olympic Games, and not every country in the world is trusted with something like that," he says.

In Sevastopol, officers listened sullenly as Berezovsky tried to entice them over to the newly proclaimed Crimean fleet he now heads – assuring them they would retain their ranks and that there would be no interruption of salary payments. "Viktor Yanukovych is the legitimately elected president of Ukraine," he told them, arguing there would be no breach of oath if they served Crimea. "The seizure of power in Kiev was orchestrated from abroad," he said.

Timur, a Ukrainian frigate captain who declined to give his last name for fear of threats to his family, said: "I will stay true to my oath and I am sure this is also true of my fellow officers."

Not helping matters is the fact that despite the fact that the well-organised and heavily armed troops are arriving in vehicles with Russian military plates and introducing themselves inside the bases as Russians, a bizarre pretence is still being maintained that the men are some kind of locally inspired volunteer unit.

At Bakhchisarai, Vladimir Mertsalov, a representative of Crimea's newly proclaimed authorities, said he had no idea who the Russian troops were. "I don't know if they are Russians. I can't tell you who they are, I have no idea, I haven't asked them, but all I know is that they are guaranteeing our security here," he said.

Later, in Sevastopol, the head of the local branch of the pro-Russian "Russian Bloc" party, Vladimir Tyunin denied there were any Russian forces present. "Where are Russian troops here? These are our local self-defence units," he said, pointing to the masked and heavily armed soldiers standing behind him in front of the Navy HQ gates.

Sergei Markov, a Kremlin-linked analyst and member of Russia's public chamber who was in Crimea for consultations with local leaders, said late on Monday he expected pressure on the soldiers to increase in the coming days.

"I don't think it will be military action, but in today's Ukraine, words are not enough. If they stay here and remain loyal to the illegal Kiev government, it will be made more and more uncomfortable for them. They need salaries, water, electricity. They need to decide where they want to live."

• This article was amended on Tuesday 4 March 2014 to include more details about Igor Nikolayevich Turchinyuk's position, the alleged involvement of Viktor Yanukovych and the quote from Sergei Markov.