(CNN) -- A Ukrainian military plane was shot down by militants near Yenakievo, in Ukraine's Donetsk region, on Thursday, a Ukrainian government counter-terrorism official said. Russian President Vladimir Putin has named a new target as global sparring over Ukraine grows: food.
In a decree signed Wednesday, Putin banned food and agricultural imports from countries that have imposed sanctions against his country.
Russian Prime Minister Dmitry Medvedev spelled out some of the details on Thursday.
Medvedev said that Russia has imposed a ban on supplies of beef, pork, fruit, vegetables, poultry, fish, cheeses and milk from the European Union, the United States, Australia, Canada and Norway.
The retaliatory move comes more than a week after the United States and European Union increased economic sanctions on Moscow for supporting pro-Russian separatists fighting Ukraine government forces in the eastern regions of Donetsk and Luhansk, along the border with Russia.
A list of specific products and food bans is still being worked out by the Russian government, according to the decree, which describes the order as a special economic measure "aimed at ensuring the security of the Russian Federation."
Russia is Europe's largest importer in value of animals, meat, dairy products, fruits and vegetables, according to the European Union.
And goods from the EU represent 16% of all Russian imports, EU numbers show.
Putin said measures would be taken to prevent a jump in food prices in Russia.
A senior U.S. administration official told CNN a ban in imports will only deepen Russia's international isolation and work against the country's own economic interest.
"Russia's Central Bank yesterday pointed out that bans on imported food will push up Russia's already high inflation rate, eroding the purchasing power of Russian citizens," the official said.
The United States insists that sanctions against Russian businesses and individuals are having an effect and have already weakened Russia's economy.
"Sanctions are working as intended in putting enormous pressure and strain on the Russian economy. ... The economy has ground to halt," U.S. President Barack Obama told reporters on Wednesday.
If Putin doesn't push to resolve problems in eastern Ukraine through diplomacy and peaceful means, Obama said, "he's going to be hurting his economy and his own people over the long term."
But so far, Obama said, violence in Ukraine hasn't stopped even as sanctions against Russia have increased.
"The issue is not resolved yet," he said. 'You still have fighting in eastern Ukraine. Civilians are dying."
Russia has denied allegations that it's supporting separatists in Ukraine and maintains that it wants to see a diplomatic solution to the crisis. But U.S. and Ukrainian officials have accused Russia of saying one thing while doing another -- building up troops along the border and continuing to send support to pro-Russian separatists.
Several countries imposed sanctions on Moscow after Russia annexed Crimea in March, which escalated the Ukraine conflict following the ouster of pro-Moscow President Viktor Yanukovych a month earlier.
Since then, tensions have simmered and flared in Ukraine, with frequent battles between Ukraine government forces and pro-Russia separatists in the eastern part of the country.
NATO Secretary General Anders Fogh Rasmussen warned Russia Thursday that any further intervention in Ukraine "would lead to further isolation" and "deeper, more profound, tougher economic sanctions that would really hurt the Russian economy."
Rasmussen told reporters in Kiev he hopes that Russia, which according to NATO has 20,000 troops along the border with Ukraine, "steps back because it wouldn't be in Russia's interest to intervene further."
MH17 search efforts halted
The apparent shootdown of Malaysia Airlines Flight 17 last month over eastern Ukraine exacerbated the situation.
U.S. and Ukrainian officials allege that a Russian-made missile shot down the plane from rebel-held territory, killing all 298 people on board. Russia and the rebel fighters deny involvement.
On Wednesday, an international team of experts, led by the Netherlands, announced a halt in its efforts to search the debris site for remaining human remains amid fierce fighting in the area.
Ukraine's government said Thursday that it was scrapping a cease-fire around the crash site -- put in place to enable the team's work -- until their mission restarts. In a statement on the Cabinet website, it accused the rebels of provocations and of putting the experts' lives at risk.
Dutch Prime Minister Mark Rutte told reporters Wednesday that search teams plan to return to the plane crash site. But he didn't give a date for when that might happen.
"We have done what we could do in the current conditions," Rutte said. "Everyone will agree with us that we should not expose our people to unnecessary risk."
The statement from Ukraine's Cabinet said at least three more zones where debris lies scattered remain unexamined.
The experts plan to discuss when the next stage of the search operation might begin shortly, it said. Until the decision is made, most will leave Ukraine, but coordination and communication teams will stay.
Rebel leader resigns
On the same day Ukraine ended the cease-fire, a major rebel leader in the Donetsk region said he was resigning his post.
Alexander Borodai, prime minister of the self-proclaimed Donetsk People's Republic, announced his resignation Thursday. He handed the position to Alexander Zakharchenko, a little-known militia commander and deputy minister of interior, who sat next to him during the announcement in Donetsk.
Details about Borodai's resignation weren't immediately available.