Kiev, Ukraine (CNN) -- Pro-Russia demonstrations were planned for Sunday in Ukrainian cities, as Russian forces continued consolidating their control over Crimea over the weekend.
But the shows of favor for Moscow are to take place outside the peninsula -- in cities in Ukraine's south and east, where there are many ethnic Russians.
On Saturday, six Russian special forces' armored personnel carriers broke through the gates of Belbek Airbase, firing warning shots into the air, a spokesman for Ukraine's Ministry of Defense in Crimea, told CNN.
One journalist was injured in the attack, said Vladislav Seleznev.
Once inside, the Russians lined up the Ukrainians in one place, he said.
In a separate incident, pro-Russian self-defense forces stormed the Novofederoskoe military base, also in Crimea, taking control of it, a Ukraine defense ministry spokesman said Saturday.
Seleznev also claimed that Crimean self-defense forces and Russian special forces took another Ukrainian ship, the Slavutych.
The ship was captured "after a two-hour assault," he said, though the Ukrainian ship's crew members came ashore and didn't suffer any injuries.
Ukrainian forces on the base threw smoke bombs during the incident and retreated to the base's headquarters, according to Seleznev, in a Facebook posting.
The base's aviation brigade then sang the Ukrainian national anthem, lowered the Ukrainian flag and left the base, he said.
The White House reacted by urging Russia to open talks with the Ukrainian government.
But in a statement, it also held the Russian military directly responsible for any casualties inflicted on Ukrainian military members -- whether from regular Russian troops or militias not wearing insignias.
The incidents occurred as international observers were set to arrive in Ukraine to monitor the security and human rights situation in a posting expected to last at least six months.
But they will not enter the contested region of Crimea, a statement from the Russian Foreign Ministry said, because this "became part of Russia."
Moscow annexed the territory following a controversial snap referendum there last week that produced an overwhelming majority of votes in favor of leaving Ukraine to join Russia.
The Organization for Security and Cooperation in Europe will eventually deploy a total of 100 observers throughout Ukraine in hopes of "reducing tensions and fostering peace, stability and security." They will also check that the rights of ethnic minorities are being protected.
The OSCE may widen the mission to include 400 more monitors, and extend it for a second six-month period if requested by the Kiev government.
Russia, which is one of the OSCE's 57 member states,approved the mission, according to state-run Russian news agency, RIA Novosti.
Russia's Foreign Ministry said it hoped the observers' work would stop nationalist extremists, which Moscow has said has a strong influence on Kiev's government, and protect linguistic rights.
Many Ukrainians speak Russian as their native language.
Russia has previously said it reserves the right to enter Ukrainian territory to protect ethnic Russians from what it says is a threat from ultra-nationalists and fascists.
Meanwhile, European leaders have demanded that independent monitors be granted access to the Crimean peninsula.
OSCE monitors made multiple attempts to enter Crimea during the height of the crisis when pro-Russian militias took control of the region. But armed men at the borders turned them back.
Claims on Crimea
Ukraine, the United States and other Western powers maintain that the Black Sea peninsula is still a part of Ukraine.
"We must not allow a new division of Europe," German Foreign Minister Frank-Walter Steinmeier said Saturday in Kiev, where he met with with Ukrainian Prime Minister Arseniy Yatsenyuk and acting President Oleksandr Turchinov.
Russia insists that its actions are legitimate. Crimea had belonged to Russia until 1954, when it was given to Ukraine.
The region also has a majority ethnic Russian population and other long historical ties to Russia.
Russia's Black Sea Fleet is based in the Crimean city of Sevastopol, making it strategically important to Moscow.
Moscow has doggedly pursued its own course even as Western leaders have denounced its actions as violations of Ukraine's sovereignty and a breach of international law.
U.S. President Barack Obama plans to meet with leaders of the G7 group of industrialized nations next week to discuss Ukraine.
Russia has been excluded from the talks on the sidelines of a nuclear summit in the Netherlands.
A planned EU-Russia summit has also been canceled, as the West seeks to increase Moscow's isolation over its actions in Ukraine.
EU leaders imposed a new round of sanctions against 12 individuals last week, bringing the total number of people facing EU asset freezes and travel bans to 33.
The United States announced its own new round of sanctions last week against 20 individuals and a bank which U.S. officials say is linked to Putin and senior Russian officials. Washington had already announced sanctions on 11 individuals.
The United States is keeping a wary eye on the large-scale drills Russia's military are conducting near Ukraine's eastern border with the country.
"The Russians have stated that they are intending military exercises," said National Security Adviser Susan Rice said. But Washington is skeptical, given recent actions, she said.