KIEV, Jan. 21 - President Petro Poroshenko accused Russia on Wednesday of sending 9,000 troops to back separatist rebels in the east of his country, and the IMF chief said she backed extra financial help for Kiev as the conflict inflicts severe economic damage, Reuters reported.

Moscow challenged Poroshenko to present facts to prove his allegations. However, he won support from NATO, which said the amount of heavy military equipment used by Russian troops in eastern Ukraine had increased, and the alliance repeated its call for the forces to withdraw.

Speaking at the World Economic Forum in Davos, Poroshenko made one of Kiev's boldest assertions yet that Russia's military is directly involved in a conflict in which more than 4,800 people have died since last April.

Russian troops were backed by a range of heavy weapons, including tanks, heavy artillery and armored vehicles, he said, adding: "If this is not aggression, what is aggression?"

Poroshenko also called on Moscow to comply with a peace plan agreed in Minsk, Belarus, last September between Ukraine,Russia and pro-Russian separatist leaders to end the conflict.

"The solution is very simple -- stop supplying weapons ... withdraw the troops and close the border," he said. "If you want to discuss something different, it means you are not for peace, you are for war."

The Minsk plan provides for a ceasefire and the withdrawal of foreign fighters and military equipment from Ukraine. But the ceasefire has been very shaky from the start and hundreds of people have died since September in clashes Kiev says have involved regular Russian troops.

Russian Foreign Minister Sergei Lavrov tried to fend off the accusations, saying he hoped for progress at talks on the conflict on Wednesday despite the renewed fighting.

"If you allege this so confidently, present the facts. But nobody can present the facts, or doesn't want to," Lavrov told a news conference before heading to the peace talks in Berlin with the foreign ministers of Ukraine, Germany and France.

German Chancellor Angela Merkel, however, warned against expecting too much from the talks. "I don't want to get hopes up too much," she said. "It is clear that the ceasefire is getting more and more fragile."

In Brussels, NATO Secretary-General Jens Stoltenberg told a news briefing that the Western alliance had monitored Russian troops in Ukraine for several months and seen an increase lately in numbers of tanks, artillery pieces and other heavy equipment.

Ukraine's economy has been pushed close to bankruptcy by the war with the rebels, and economists have warned of debt writedowns if an existing IMF loan program is not beefed up to plug a estimated $15 billion funding gap.

Poroshenko told IMF Managing Director Christine Lagarde at a meeting in Davos that his government had appealed for more funding. "President Poroshenko informed me today that the Ukrainian authorities have requested a multi-year arrangement with the Fund ... to replace the existing Stand-By Arrangement," she said in a statement.

Lagarde said the IMF board would discuss the request, and made clear that Ukraine would have to make broad and deep economic reforms in return for any deal. However, she told reporters: "I will submit it to the board which will convene as soon as possible. I will propose to support it."

Also in Davos, Ukrainian Finance Minister Natalia Yaresko told Reuters she was hopeful that a deal with the International Monetary Fund would be reached in the very near future.

Asked if $15 billion would be enough to pull Ukraine out of economic crisis, Yaresko emphasized the urgent need for an IMF decision. "The main thing is that we need a decision. And front-loading is very important. Any number, if it is dribbled out over a long period of time, might not be sufficient," she said.

The existing IMF package, agreed in April last year, is worth $17 billion and has so far paid out $4.6 billion in two installments.

The collapse in Ukraine's hard currency reserves to enough to cover only five weeks of imports is threatening to force Ukraine into extending debt maturities or even writing down government debts, but Yaresko said: "It is our intention to meet our obligations." (rt/ez)