SIMFEROPOL, Crimea — Russia said Monday it was pulling a battalion of several hundred troops away from the Ukrainian border but kept tens of thousands in place, prompting a worried response from the Kiev government about what the U.S. warned was still a "tremendous buildup."
Russia moved quickly to strengthen its economic hold on Crimea, with Prime Minister Dmitry Medvedev arriving in the newly annexed peninsula with promises of funds for improved power supplies, water lines, education and pensions for the elderly.
Russia's takeover of the strategic Black Sea region, its troop buildup near Ukraine's border and its attempts to compel constitutional changes in Ukraine have markedly raised tensions with the West and prompted fears that Moscow intends to invade other areas of its neighbor.
However, Russian President Vladimir Putin told German Chancellor Angela Merkel in a phone call Monday that some troops were being withdrawn from the Ukraine border, Merkel's office said. The withdrawal involved a battalion of about 500 troops, Russian news reports said.
The U.S. reacted cautiously to the Russian troop movement, with Secretary of Defense Chuck Hagel saying that "tens of thousands" of Russian forces still remained along the Ukrainian border, a situation he called "a tremendous buildup."
The new government in Ukraine said the action only increased its uneasiness about Russia's intentions.
"We have information that Russia is carrying out incomprehensible maneuvers on the border with Ukraine," Ukrainian Foreign Ministry spokesman Yevgen Perebyinis said. "Troops in some places are moving backward, some of them are moving forward. Which is why, obviously, we are worried by these movements of armed forces. We have no clear explanation from the Russian side about the aim of these movements."
Russian Foreign Minister Sergey Lavrov and U.S. Secretary of State John Kerry also discussed Ukraine by phone Monday, a day after holding talks in Paris, the Russian foreign ministry said.
A senior U.S. official said Lavrov had promised Kerry that a division of Russian troops would be pulled back; a division generally consists of thousands of troops.
"Now there have been reports of possible drawdowns of Russian military forces from the border. We haven't seen that yet, but if they turn out to be accurate, that would be a good thing," White House spokesman Jay Carney said.
Concerns of a possible invasion of eastern Ukraine — home to many ethnic Russians — were stoked by the large numbers of troops Russia had along the Ukrainian border for what Moscow said were military exercises.
One Russian battalion — about 500 troops — that had been sent to the Rostov region next to Ukraine was being withdrawn to its permanent base in the central Samara region, Russian news agencies quoted the Defense Ministry as saying Monday.
Alexander Rozmaznin, deputy chief of the Ukrainian armed forces command center, also confirmed a drop in Russian troop numbers along the border.
In Kiev, meanwhile, Ukraine's acting president flatly rejected escalating Russian pressure to turn Ukraine into a loose federation.
"Russia's leadership should deal with problems in the Russian Federation, and not with Ukraine's problems," Ukraine's acting president Oleksandr Turchinov said. "It is Ukrainians that should dictate the form of the new constitution and how the country is structured."
Medvedev, who led a delegation of Cabinet ministers on a surprise visit to Crimea, pledged that Russia would quickly boost salaries and pensions and pour in resources to improve education, health care and local infrastructure.
But making no mistake about Russia's view of the peninsula, Deputy Prime Minister Dmitry Rogozin tweeted a photo of himself upon arrival with the words "Crimea is ours, and that's that."
Russia's defense minister, meanwhile, announced that all Crimean men of conscription age will get a deferral from the draft for one year.
Russia annexed Crimea from Ukraine in March after a hastily called referendum just two weeks after Russian forces took control of the Black Sea region. Ukraine and the West have rejected the vote.
The annexation came after Ukraine's president, Viktor Yanukovych, was ousted in February and fled to Russia following months of protests. Russia claims the ouster was a coup and that the new Ukrainian authorities are nationalist fascists who will abuse Ukraine's large ethnic Russian population.
To keep its influence over eastern and southern Ukraine, Russia has pushed for Ukraine to become a federation where regions would have broad powers. The U.S. says it's up to Ukrainians to determine the structure of their government, not Moscow.
Medvedev said Russia will create a special economic zone in Crimea — a peninsula of 2 million people — that will include incentives for business with lower taxes and simpler rules, and will develop the region as a top tourist destination.
"We must create a new investment history for Crimea, which will be more successful than what it has been," Medvedev said.
Medvedev particularly emphasized the need to ensure a stable power supply for the peninsula. Crimea currently gets about 80 percent of its electricity and a similar share of its water from Ukraine, and power cutoffs last week raised fears that the Ukrainian government could use energy as a weapon to bargain with Russia.
Medvedev said Russia already has made sure that Crimea has enough backup power capacity to ensure an uninterrupted electricity supply. He added that Russia will work on long-term solutions to Crimea's energy problem that could involve linking the region to Russia's power grid or developing local power generation.
In Kiev, a member of the radical nationalist group Right Sector was detained late Monday over his involvement in a shooting near a restaurant adjacent to Independence Square, which saw many of the protests that culminated in Yanukovych's ouster. Many activists have remained encamped there and have signaled their intent to remain until the election of what they deem to be a legitimate government.
Officials said a city government official was among three people injured in the incident. Police later surrounded the Dnepr hotel in central Kiev, which Right Sector has commandeered as it headquarters, in an effort to persuade the group to hand over any weapons in its possession.
Isachenkov reported from Moscow. Associated Press writers Jim Heintz in Moscow, Nedra Pickler in Washington and Matthew Lee in Tel Aviv, Israel, contributed to this report.