Russia claims that troops that have taken over Ukraine's Crimea peninsula are "self-defense forces created by the inhabitants of Crimea" and that they "have no authority over them."

But an increasing number of Russian soldiers are riding in on Russian armored vehicles into the strategic Black Sea peninsula.

For more than a week, Russian troops wearing uniforms without insignia have been commandeering Ukrainian military facilities and urging besieged Ukrainian soldiers to defect.

Armed men, believed to be Russian soldiers, walk near the Ukrainian naval base at the Crimean port of Yevpatorya March 8, 2014. REUTERS/David Mdzinarishvili

The Russians tightened their grip on Sunday, sealing off a military airport on Crimea's west coast and capturing a nearby Ukrainian border post with 15 personnel inside. On Monday, they took over a military hospital and a missile base.

Russian forces now control 11 border guard posts across Crimea, and have issued several ultimatums for the Ukrainians in bases to surrender or be stormed.

The demands have passed without serious incident, but the Ukrainians are still blocked in.

Here are some disquieting scenes from the occupation:

There are about 20,000 Russian soldiers in Crimea.

Uniformed men, believed to be Russian servicemen, walk in formation near a Ukrainian military base in the village of Perevalnoye outside Simferopol, March 6, 2014. REUTERS/Vasily Fedosenko

Hiding in plain sight.

A uniformed man, believed to be a Russian serviceman, stands guard near a Ukrainian military base outside the city of Sevastopol, March 7, 2014. REUTERS/David Mdzinarishvili

The two sides converse and trade cigarettes.

A Ukrainian serviceman (rear L) gives a cigarette to a uniformed man (R), believed to be a Russian serviceman, at a Ukrainian military base in the village of Perevalnoye, outside Simferopol, March 6, 2014. REUTERS/Vasily Fedosenko

But that's all part of the siege.

A Ukrainian serviceman watches uniformed men, believed to be Russian servicemen, passing by at a Ukrainian military base in the village of Perevalnoye outside Simferopol, March 6, 2014. REUTERS/Vasily Fedosenko

The Ukrainians are treated as "occupiers" and hostages in their own bases.

A Ukrainian serviceman talks on the phone at a Ukrainian military base in the village of Perevalnoye, outside Simferopol, March 6, 2014. REUTERS/Vasily Fedosenko

"They are putting psychological pressure on us," Lieutenant Colonel Alexander Lomaka told Reuters from a military base on the coast of western Crimea. "We have no fight with them, but we are not going to hand over our weapons to soldiers of the Russian Federation."

Ukrainian servicemen look out of the gate of their military base near Sevastopol, March 8, 2014. REUTERS/Baz Ratner

Russia has deliberately sunk three of its own ships to block Ukraine's navy.

An abandoned naval ship sunk by the Russian navy to block the entrance is seen in the Crimean port of Yevpatorya March 8, 2014. REUTERS/David Mdzinarishvili

Ukrainian sailors, completely blocked in, are smuggling food onto their warships.

Ukrainian sailors stand guard on top of a Ukrainian navy ship at the Crimean port of Yevpatorya March 8, 2014. REUTERS/David Mdzinarishvili

And waiting for the superior fleet of Russia to make its next move.

A Ukrainian sailor stands guard on top of a Ukrainian navy ship at the Crimean port of Yevpatorya March 8, 2014. REUTERS/David Mdzinarishvili

Russian troops roam outside all key military installations.

An armed man, believed to be a Russian serviceman, stands guard outside an Ukrainian military base in the village of Perevalnoye near the Crimean city of Simferopol March 9, 2014. Shots were fired in Crimea to warn off an unarmed international team of monitors and at a Ukrainian observation plane, as the standoff between occupying Russian forces and besieged Ukrainian troops intensified. REUTERS/Thomas Peter

And pro-Russian "self-defense forces" are mobilizing within the peninsula.

Members of a pro-Russian self defence unit stand in formation as they take an oath to the Crimea government in Simferopol March 8, 2014. REUTERS/Vasily Fedosenko



Here are some of the scenes from last week:

Ukrainian soldiers, left watch as a Russian soldier guards the gate of an infantry base in Perevalne, Ukraine, Tuesday, March 4, 2014. AP/Darko Vojinovic

Ukrainian soldiers watched as Russian soldiers surrounded them.

A Russian soldier lies with his back to Ukrainian fighter jets as he watches Ukrainian serviceman at the Belbek airport in the Crimea region March 4, 2014. REUTERS/Baz Ratner

Belbek airport was especially tense. Here's a Russian soldier looking through the sights of his weapon. A Russian soldier looks through the sights of his weapon as Ukrainian servicemen wait at Belbek airport in the Crimea region March 4, 2014. REUTERS/Baz Ratner The vehicles and weaponry on the Russian side are substantial. A Russian serviceman guards the Belbek airport in the Crimea region March 4, 2014. REUTERS/Vasily Fedosenko

The Ukrainian soldiers at Balbek marched in defiance of the siege. Ukrainian servicemen carry flags as they leave Belbek airport in the Crimea region March 4, 2014. REUTERS/Baz Ratner Soldiers under Russian command tracked them. Here's one aiming a rocket-propelled grenade launcher. A soldier under Russian command aims a rocket propelled grenade launcher at a group of over 100 hundred unarmed Ukrainian troops who appeared at the Belbek airbase, which the Russian troops are occcupying, in Crimea on March 4, 2014. Sean Gallup/Getty When they got closer, the soldiers shouted and warning shots were fired in the air. Russian soldiers fire warning shots at the Belbek air base, outside Sevastopol, Ukraine, on Tuesday, March 4, 2014. AP/Ivan Sekretarev Another soldier restrained his colleague after he fired his weapon. A soldier under Russian command restrains a colleague after he fired his weapon into the air and screamed orders to turn back at an approaching group of over 100 unarmed Ukrainian troops at the Belbek airbase. Sean Gallup/Getty Here a Russian serviceman is seen behind pro-Russian "self-defense forces" at Belbek. A Russian serviceman is seen behind pro-Russian activists at the Belbek Sevastopol International Airport in the Crimea region March 4, 2014. REUTERS/Vasily Fedosenko Russian forces are also blockading Ukrainian ships. Ukrainian sailors, who have been blocked in their own dock for six days, have to get shipments of food. Russian soldiers guard a pier where two Ukrainian naval ships are moored, in Sevastopol, Ukraine, on Wednesday, March 5, 2014. AP/Andrew Lubimov And there's a Russian tank blocking the road near the small Ukrainian city of Armyansk, which connects Crimea with the rest of Ukraine.

A tank belonging to the Russian forces guards a check-point set up by Russian forces on a road near the small Ukrainian city of Armyansk on the Crimean peninsula, on March 5, 2014. Alexey Kravtsov/AFP