Armed men, believed to be Russian servicemen, take cover behind an armored vehicle as they attempt to take over a military base in the Crimean town of Belbek, near Sevastopol.

March 22, 2014 Armed men, believed to be Russian servicemen, take cover behind an armored vehicle as they attempt to take over a military base in the Crimean town of Belbek, near Sevastopol. Shamil Zhumatov/Reuters

After an ultimatum to abandon the base and an hours-long standoff, Russian troops in at least four armored vehicles seized control of one of the last Ukrainian military outposts in Crimea.

Russian President Vladimir Putin on Friday signed legislation to complete the annexation of Crimea, just hours after the first signs emerged in Russia of the bite from U.S. sanctions.

Russian President Vladimir Putin on Friday signed legislation to complete the annexation of Crimea, just hours after the first signs emerged in Russia of the bite from U.S. sanctions.

— With a burst of automatic weapons fire and stun grenades, Russian forces in armored personnel carriers on Saturday broke through the walls of one of the last Ukrainian military outposts in Crimea, then quickly overpowered Ukrainian troops armed only with sticks.

The fall of the Belbek air base, along with the loss of a second Ukrainian air base Saturday near the Crimean town of Novofedorivka, removed one of the last barriers to total Russian control of the Crimean Peninsula.

It came less than a week after Crimeans voted overwhelmingly in a referendum to leave Ukraine and join Russia. In their speed, the base takeovers— which had progressed all week — were emblematic of Crimea’s swift absorption into the Russian Federation, even as Ukraine’s leaders reiterated Saturday that they do not recognize the annexation.

In Belbek, the Ukrainians put up no resistance on the orders of the base commander, Col. Yuli Mamchur, who has become a symbol of Ukrainian spirit for his steely defiance of repeated Russian demands that the tactical air wing surrender and relinquish all weapons.

Most of the 200 or so troops on the base have weapons, but Mamchur was determined to avoid casualties. So when four Russian personnel carriers drove through a concrete wall and rammed down the wrought-iron front gate after an hours-long standoff, Mamchur’s men were waiting with sticks that appeared to have been fashioned from broken broom handles, tree branches, railing dowels, table legs and croquet mallets.

A Russian armored vehicle attempts to enter Belbek air base in Crimea where Ukrainian forces are resisting handing over control. (Reuters)

Two ambulances sped from the scene within minutes of the Russian incursion. Mamchur said one of his men had been kicked and beaten by the advancing Russians. It was unclear whether there were other casualties.

Russian infantrymen armed with automatic rifles rushed through the two gaping holes in the wall and shouted for the Ukrainians gathered outside the base headquarters building to move back. The Ukrainians stood their ground and responded with a stream of Russian curse words.

“We have done everything we could,” Mamchur told the men and women in his command. “You acted with honor. There is nothing we should be ashamed of.”

Then the Ukrainians lined up two deep and sang the Ukrainian national anthem.

The storming of the Belbek installation capped a surreal day characterized by spurts of melancholy, boredom, joy and calculated preparations for a takeover.

At 8:30 a.m., smoke wafted over the base near Sevastopol as soldiers tossed documents into two bonfires at the perimeter. Troops milled around killing time before a confrontation they knew was inevitable. One serviceman sat on a wall picking out a Beethoven melody on a piano app on his phone, “to lighten the mood,” he said.

When a group of Russians arrived to talk with Mamchur, he refused to allow them onto the base and instead walked out to meet them on a street corner. He leaned against a faded yellow taxi as the Russians urged him to give up weapons and allow his troops to depart along a planned safe corridor.

Residents of a nearby village gathered on the rise of a hill to watch. Several men shouted anti-gay slurs at the Ukrainian commander. A woman berated him loudly for having an armed security detail. Posters have appeared near the base saying that Mamchur should be executed. Some people shouted that he was hiding behind his troops to advance his own career. One man said the real commander was Mamchur’s wife.

Mamchur said he had no contact with the government in Kiev and was making decisions on his own. Several Ukrainian troops said they feel ignored and abandoned by the military leadership.

After the talks concluded with no agreement, Mamchur returned to the base to officiate at the wedding of the two lieutenants in his command. Both the bride and the groom wore blue jeans and black jackets, and more than 100 troops lined up to fete them with champagne, chocolates, figs and cookies.

“I am very happy you decided to marry now, and here,” Mamchur told them, then popped the first cork and danced with the bride’s best friend.

Soon another Russian officer appeared at the gate to deliver an ultimatum demanding that the Ukrainians surrender their weapons and abandon the base. They had one hour, Mamchur said he was told.

But one hour stretched into two and then three, as Russian vehicles rolled into position, visible from a distant hilltop. Women and elderly men from the village moved close to the fence and swore at the Ukrainian soldiers patrolling the perimeter. One elderly man tore down a “no trespassing” sign, angrily ripped it to pieces and tossed the pieces over the fence.

Uniformed men standing shoulder to shoulder suddenly appeared outside the gate. They seemed to be a mix of Russian regular troops wearing balaclavas and carrying sophisticated weaponry, Cossacks in fur hats, and unarmed pro-Russia militiamen. But when the assault began at 4:45 p.m., the force was all Russian regulars.

It took seconds for the armored vehicles to slice through the concrete walls, followed by a rush of infantrymen. Gunfire and the percussion boom of stun grenades filled the air.

“Why did you shoot?” one Ukrainian demanded angrily. “We didn’t fire a single round.”

“This is already Russia,” one Russian soldier shouted at the Ukrainian troops who refused to obey his order to move.

Ukrainian flags were still flying from the gatehouse and the flagpole outside base headquarters when journalists were rounded up and led away after having some of their camera equipment confiscated. The Russian banner was certain to replace those flags.

The Ukrainian ship Slavutych in Sevastopol harbor was also stormed Saturday evening by a combination of Russian special forces and the Crimean “self defense” units they cooperate with, said a defense ministry official.

Vladislav Seleznyov, a ministry spokesman, said the incursion lasted two hours. The Slavutych has been boxed in for more than three weeks, unable to leave because the Russian Navy sank a ship at the entrance to the bay.

He also said that a Ukrainian ship in Donuzlav Bay connected to the Black Sea, which also is blocked in by a sunken ship at the entrance, remains in Ukrainian hands.

The base and ship takeover came as Russia said it would not allow access to Crimea for international monitors who are being dispatched to Ukraine. Up to 400 monitors are to deploy across the country, including in Ukraine’s volatile south and east. Clashes in those areas in recent weeks between pro-Russian and pro-Ukrainian demonstrators have turned deadly. Pro-Russian rallies were held in the eastern Ukrainian cities of Donetsk and Kharkiv on Saturday.

The European Union, following the lead of the United States, added a dozen names Friday to its list of Russian officials subject to visa and financial restrictions. But efforts by eastern members of the E.U. to pursue much tougher measures were rebuffed by leaders of bigger countries worried about the consequences on their economies.

The Russian Foreign Ministry on Saturday called Europe’s moves “divorced from reality” and said Russia reserves the right to respond.

Englund reported Moscow. Griff Witte in London and Kathy Lally in Kiev, Ukraine, contributed to this report.