Tensions remain high in Ukraine's Crimean peninsular after Russian soldiers fired warning shots into the air when around 300 Ukrainian troops demanded access to the seized Belbek airbase in the region.

The tense stand-off erupted on the same day as Russian media reported the state had successfully test-fired an Intercontinental Ballistic Missile (ICBM).

The RS-12M Topol missile was fired from a land-based mobile launcher in the southern Astrakhan region near the Caspian Sea.

Citing a Russian defence ministry spokesman, state-run news agency RIA said the dummy warhead hit its target at an airfield in Kazakhstan. The US was informed of Tuesday's test in advance, before the build-up of tensions in the Crimea.

The last time Moscow test-fired an ICBM was in October 2012 from Plesetsk in northern Russia.

Sky's Katie Stallard said it "was sending a not very subtle message that Russia has military might in the region".

"Russia still considers this part of its sphere of influence, and Russia is very clear that it is calling the shots in this situation," she said.

"But what we saw at the Belbek airbase was how dangerous a game this can be and how much of this now comes down to the individuals on the ground.

"These men who are face to face, metres apart. A wrong move, a wrong order a misinterpreted signal on the ground could be all it takes to turn this from a stand-off into something much more significant, much more dangerous."

At the Belbek airbase in Sevastopol, around a dozen Russian soldiers warned the unarmed Ukrainian servicemen to back away as they tried to take their positions back.

The Russians then fired several shots into the air and threatened to shoot the Ukrainians.

A video of the confrontation showed a Russian soldier saying to the Ukrainians: "I want your officer here. We'll be shooting your legs."

A Ukrainian soldier then responded: "You will pay for this. You'll be responsible."

"America stands with us," another Ukrainian soldier added.

Speaking from the airbase, Stallard said wives and mothers of the Ukrainian servicemen had gathered between the two lines to prevent any bloodshed.

She said: "There are around a dozen women, wives and mothers standing in front of their men because they believe they (Russian soldiers) will be more reluctant to fire on them."

Some 16,000 Russian troops are on the ground in the region - a move the US said was a clear violation of international law.

Russian President Vladimir Putin has ordered troops taking part in military exercises close to the Ukrainian border in western Russia to return to their bases.

But hundreds of Russian soldiers remain at a military base near the Crimean capital Simferopol, preventing Ukrainian soldiers from going in or out.

Russian forces have also reportedly seized a border checkpoint on the Ukrainian border between Russia and Crimea.

Earlier, Mr Putin spoke for the first time since the crisis began and warned he would use "all means" to protect Russian citizens against what he called an "unconstitutional coup" in Ukraine.

It also came as US Secretary of State John Kerry arrived in Kiev for talks and pledged an aid package including $1bn in loan guarantees to Ukraine.

He condemned Russia's "invasion" of Ukraine and called on Russia to return its troops to their barracks after escalating tensions in the Crimea region of the country.

British Foreign Secretary William Hague made it clear he had no doubt the troops in Crimea were acting on orders from Moscow, despite claims by Mr Putin they were "local self-defence forces".

Moscow's UN envoy told a stormy meeting of the UN Security Council Ukraine's ousted leader Viktor Yanukovych had sent a letter to Mr Putin requesting he use Russia's military to restore law and order in Ukraine.

Russian ambassador Vitaly Churkin, reading from an unofficial translation of the letter he said was dated March 1, said: "The country has plunged into chaos and anarchy.

"The country is in the grip of outright terror and violence driven by the West. People are persecuted on political and language grounds.

"In this context, I appeal to the President of Russia Vladimir V Putin to use the armed forces of the Russian Federation to re-establish the rule of law, peace, order, stability and to protect the people of Ukraine."

But US President Barack Obama warned Moscow it would find itself "on the wrong side of history" - and that Russia's deployment of troops in Ukraine violated international law.

The US has suspended all military engagements with Russia over its deployment of troops in Crimea.

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