UKRAINE — Armed forces including armored vehicles have broken inside a Ukrainian airbase in Crimea, firing from automatic weapons into the air, an AFP correspondent saw.

An armored vehicle rammed through the gate of the Belbek base, which has long been under siege by Russian-allied forces, and an ambulance was also seen approaching with sirens blaring, as armed men went inside and pointed guns at Ukrainian soldiers.

A man in camouflage and sunglasses dismantled a camera that provided a live feed of the front gate to the base. AFP reporters saw at least three armored personnel carriers enter the airbase.

The Ukrainian commander of the base, Yuliy Mamchur, said there was at least one injury in the assault. He called his men together, they sang the Ukrainian national anthem and then stood at ease. He said they were going to turn over their weapons.

The Belbek air force base had been the biggest base still holding out against Russia’s creeping month-long invasion.

Earlier Saturday the base wrote on its website that troops inside had received an ultimatum from Russian forces to lay down their weapons and surrender or prepare to be stormed.

The base is stormed by a Russian armored vehicle at the 3:30 minute mark

The assault followed a Russian takeover of Ukraine’s only submarine in Crimea, the Zaporozhye. Troops took control of the vessel and raised the Russian navy flag over it, the Russian Black Sea Fleet said on Saturday.

“The former Ukrainian submarine Zaporozhye was moved about an hour ago to join the Russian Black Sea Fleet’s submarine division,” fleet spokesman Vyacheslav Trukhachyov told AFP.

The Ukrainian flag on the submarine was replaced by the St Andrew’s flag, a blue cross on a white background, of the Russian navy.

Russian forces this week have taken over several Ukrainian fleet vessels as well as navy headquarters in Sevastopol, tightening their military grip on Crimea after its inclusion into Russia by the parliament in Moscow.

Also Saturday, about 200 pro-Russian protesters stormed a Ukrainian air force base in western Crimea, forcing the soldiers to leave as the Ukrainian flag was taken down.

The unarmed crowd yelling “Russia! Russia!” broke through to the base in the town of Novofedorivka and started smashing windows.

Ukrainian servicemen barricaded themselves inside buildings and threw smoke bombs at the intruders from the roof. Some of the people threw the smoke bombs back at the soldiers.

Russian officers stood outside watching as the protesters took down the Ukrainian flag and put up the Russian navy flag.

“It’s my unit and I have to protect it!” a Ukrainian soldier yelled to the Russian officers from the roof.

A Russian military officer then went inside the building to negotiate with the Ukrainians as the crowd of protesters were told to leave. Several dozen soldiers were later seen walking out of the base, leaving it empty, with Russian soldiers standing outside.

The spokesman of the Ukraine defense ministry in Crimea, Vladislav Seleznyov, cited sources at the base as saying that the attackers were mostly non-locals.

“There are some locals among the attackers, but a lot of non-locals. We do not recognize these faces,” the source from the base said, according to Seleznyov.

Ukraine’s defense ministry on Saturday said that troops returning from Crimea following Russia’s annexation of the strategic Black Sea peninsula were “heroes” and not deserters.

The ministry denied reports that “units leaving the peninsula for the mainland would be dissolved, and that Ukrainian prosecutors were pursuing soldiers for high treason”.

It said the soldiers who served in Crimea were “genuine heroes for all Ukrainians”.

Many of the thousands of Ukrainian soldiers who were surrounded by pro-Russian forces in Crimea last month have left their posts without a fight, as Moscow annexed the peninsula.

Canadian Prime Minister Stephen Harper on Saturday accused Russian President Vladimir Putin of damaging global security by sending troops into Crimea and eventually annexing the Black Sea peninsula.

Harper, the first leader from the G7 group of top industrialized powers to visit Kiev since last month’s fall of Ukraine’s pro-Kremlin regime, said the consequences of Putin’s actions “will be felt far beyond the borders of Ukraine or even the European continent itself.”

He cited a 1994 agreement under which Ukraine gave up its Soviet-era nuclear weapons in return for sovereignty guarantees from Russia and several Western powers as the reason why some nations may now decide “to arm themselves to the teeth”.

“Ukraine relinquished the nuclear weapons it inherited from the former Soviet Union on the basis of an explicit Russian guarantee of its territorial integrity,” said Harper.

“By breaching that guarantee, President Putin has provided a rationale for those elsewhere, who needed little more encouragement than that already furnished by pride or grievance, to arm themselves to the teeth.”

AP contributed to this report.