Russian President Vladimir Putin ordered officials to tighten control of the Ukraine border Tuesday after a flurry of drone attacks targeted regions inside Russia – with one drone crashing just 60 miles from Moscow.

Ukraine authorities did not take responsibility for the attacks but have claimed the right to such forays to turn back Russia's invasion. Pictures of the drone showed it was a small Ukrainian-made model with a reported range of close to 500 miles but no capacity to carry a large load of explosives.

Russian forces shot down a Ukrainian drone early Tuesday over the Bryansk region, local Gov. Aleksandr Bogomaz said in a Telegram post. He said there were no casualties. Three drones also targeted Russia’s Belgorod region along the border, and one flew through an apartment window in its namesake capital, local authorities reported.

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Moscow Regional Gov. Andrei Vorobyov said the Moscow-area drone apparently was targeting – but did not hit – a Gazprom gas distribution facility.

"There are no casualties or destruction on the ground," he said on Telegram. "There are no risks to the safety of local residents."

Developments:

►Putin followed through on last week's vow to suspend the last remaining nuclear arms treaty with the U.S., signing a bill to that effect Tuesday. Putin and Russian authorities have said they're not pulling out entirely from the New START treaty and will respect its caps on nuclear weapons and continue to notify the U.S. about test launches of ballistic missiles. 

►Air raid alarms interrupted TV and radio programming in several Russian regions Tuesday. Russia’s Emergency Ministry said in an online statement that the announcement was a hoax resulting from hacking.

►Flights in and out of the main airport in St. Petersburg, the second-largest city in Russia, were stopped for an hour Tuesday, prompting reports that an unidentified drone was the reason. The Russian military later said it was because of air defense drills.

►At least four civilians were killed and five wounded by renewed Russian shelling in the southern Ukraine city of Kherson and surrounding villages, Ukraine authorities said Tuesday.

►One-third of the Ukrainians who fled to European Union nations because of the war eventually want to return home, the same proportion as those who prefer to stay in their host country, according to nearly 15,000 respondents to a survey conducted by the EU's Agency for Fundamental Rights. About one-quarter of the respondents were undecided.

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Russian death toll surpasses all its wars since WWII

More than 60,000 Russian troops have died in the first year of the Ukraine war, more than all Russian wars since World War II combined, a new study says.

The analysis by the Center for Strategic International Studies estimates that 60,000 to 70,000 Russian soldiers have died in Ukraine. Russia suffered roughly 200,000 to 250,000 total casualties – personnel killed, wounded or missing – during the first year of the war, the analysis says.

In comparison, Russia had 13,000 to 25,000 fatalities in Chechnya from 1994 to 2009, and 14,000 to 16,000 in Afghanistan from 1979 to 1989.

"Some types of authoritarian regimes are willing to accept high casualties in interstate conflicts, but Russian casualty numbers are unprecedented for post-World War II Russia," the analysis says.

The Ukrainian military has also performed "remarkably well" against a much larger and initially better-equipped Russian military, in part because of the innovation of its forces, the analysis says. It adds that Putin has thus far been willing to accept large numbers of Russian fatalities with limited political repercussions, "but it is unclear that he will be able to do so forever."

'Grinding slog' in front lines unlikely to pick up in near future

A senior Pentagon official calls the front lines in Ukraine "a grinding slog,'' and field conditions don't augur much change in the near future, perhaps even longer.

"I do not think that there's anything I see that suggests the Russians can sweep across Ukraine and make significant territorial gains anytime in the next year or so," Colin Kahl, under secretary of defense for policy, told a House committee Tuesday.

Intense fighting continues in the eastern Donbas region as Russia tries to solidify its control, but neither side has gained much ground in the winter. The warming temperatures and softer soil of the upcoming spring don't lend themselves to major advances either.

"Both sides stay in their positions, because as you see, spring means mud. Thus, it is impossible to move forward," a Ukrainian commander identified only as Mykola told Reuters.

Tanks, but no tanks

Before their current insistence on getting fighter jets, Ukrainian leaders clamored for modern tanks to confront Russian troops. That request was finally granted Jan. 25, when the U.S. and Germany announced they had overcome their initial reluctance and would provide the vehicles, opening the door for other countries to contribute them as well.

Only they haven't done much of that.

Ukraine has asked for 300 tanks, the U.S. and its allies have pledged around 100, and few have made it to the battlefield so far. Some of the delay was expected because of the need for training and the challenging logistics of delivering the tanks -- the U.S. M1 Abrams, for example, weighs at least 60 tons.

But the same countries that pressured Germany to allow for their Leopard 2 tanks to be sent to Ukraine are running into obstacles, some based on lack of usable supply, some based on political resistance or other factors, the New York Times reported.

“Of course some nations have delivered, or at least announced that they will,” the newspaper quoted German Federal Minister of Defense Boris Pistorius saying at the Munich Security Conference this month. “But others have not done that.”

Contributing: Maureen Groppe, USA TODAY; The Associated Press

This article originally appeared on USA TODAY: Putin issues alert after drone strikes 60 miles from Moscow; Russian death toll surpasses all wars since WWII: Ukraine live updates