Russian and Ukrainian military forces continued their stand-off in several military bases across the Crimean in Ukraine again, and diplomatic tensions grew across the globe as the crisis deepened.

Families of those Ukrainian soldiers trapped inside bases today started to arrive at the gates of the stand-off to see their loved ones, and voice their protest on Russia's growing military incursion into their region.

Europe Editor James Mates reports.

Ukrainian military sources say they have been told to surrender, and two Ukrainian warships say they have been given a deadline by which to do so, or face being stormed by Russian soldiers intent on seizing the ships.

So far, the military commanders have refused to leave their bases, despite the threats, but there are concerns over how long the bases can last, surrounded and outnumbered as they are by the full strength of the Russian army.

Ukrainian defence ministry spokesman Maksim Prauta said four Russian navy ships were blocking a Ukrainian anti-submarine warship, as well as a command ship in Sevastopol's harbour.

Russian Navy ship entered the Crimean port city of Sevastopol on March 2. Credit: Reuters/Baz Ratner

Tonight, Ukrainian border guards claimed that Russian forces had seized control of the border guard checkpoint on the Ukrainian side of the ferry crossing between Crimea and Russia, and had brought truckloads of soldiers by ferry.

Read: Russia 'seizes control of Crimea border checkpoint'

Ukrainian servicemen and women gather at the gates of their military unit, in Lyubimovka, southwest of Simferopol, in the Crimea. Credit: Vasily Fedosenko/Reuters

This appears to corroborate comments made by Ukraine's acting president, who earlier today said the numbers of Russian soldiers inside the Crimea "keeps growing", and repeated his appeal to the Kremlin to "stop aggression and piracy."

Ukraine: Size of Russian forces in Crimea 'keeps growing'

Ukraine'a ambassador to the UN told an emergency meeting of the UN Security Council that Russia has deployed around 16,000 troops from Russian territory into Crimea since February 24.

Tomorrow Nato will hold an emergency meeting on the crisis, at the request of Poland, as it felt under threat from the crisis.

European leaders will also hold an emergency meeting this Thursday to discuss ways to de-escalate the crisis, and discuss the possibility of sanctions.

The meetings come as President Obama said Russia had violated international law through its military intervention, and warned that the incursion would be costly as the US government warned it will look at a serious of economic and diplomatic sanctions.

Read: Obama says Russia has violated international law in Ukraine

Prime Minister David Cameron, who spoke to Obama over the weekend, said Russia must de-escalate the situation, or face "costs and consequences."

Read: Cameron: Russian must de-escalate crisis or face 'costs'

However, snapped government documents appear to reveal that "costs" would not include actual sanctions.

The document was seen on the way into Downing Street today. Credit: @Politicalpics

A document seen being taken into Downing Street today seemed to outline the government's strategy to provide Ukraine with an alternative gas supply, should Russia cut theirs off, and that the government would "discourage any discussion of contingency military preparations" and would not support trade sanctions, or measures that may "close London's financial centre to the Russians."

More: Snapped document reveals UK strategy for Ukraine

Russia robustly defended its actions and position throughout the day, and this evening, Moscow's UN envoy said Ukraine's ousted leader Viktor Yanukovich sent a letter to Russian President Vladmir Putin requesting military assistance to restore law and order to the country.

Read: Yanukovich 'asked Russian to use forces to establish peace'

Putin did not make any comment on the crisis himself, but instead supervised a Russian military show of strength in an airfield near St Petersburg.

Vladimir Putin and Defence Minister Sergei Shoigu Credit: Reuters

Accompanied by his defence minister and various state-run news agencies, he spent the day inspecting the spectacle of the Russian military might he commands.

Putin supervises Russian military 'live fire exercise'