In a Kremlin meeting with the security chiefs of several former Soviet republics, Putin warned that the continuing war carried unpredictable destabilizing consequences and posed a serious threat to the security of the republics.
"The crisis has spilled beyond a local conflict and today has become a potential threat to the stability in other regions, including the Commonwealth of Independent States," Putin said. "The decision to launch the war has severe unforeseeable consequences, including increased extremism."
Earlier, Putin strongly condemned the war as "unjustified" and a "big mistake" and called for a quick end to military operations.
Russian Foreign Minister Igor Ivanov, summoned to address the State Duma, the lower house of Parliament, on the Iraq war, said Moscow had serious questions about U.S. plans for that country.
"We have questions about the planned military occupation of Iraq," he said. "Without corresponding resolutions of the U.N. Security Council, this occupation will be illegal."
The minister said he had unanswered questions regarding the "observation of norms of international humanitarian law in the course of the operation (in Iraq), and in particular the prohibition on attacking civilians and civilian objects, using non-precision weapons, and harming the environment."
Reiterating Moscow's opposition to the U.S.-led war against Iraq, the Foreign Ministry issued a statement decrying "the trampling of international law in the Persian Gulf and the decision to turn away from multilateral to unilateral military solutions."
Ivanov said Russia would move to protest the continuing war by asking the United Nations to determine if the United States had broken international law.
"Together with other states, we will put this question before the U.N.'s legal department," Ivanov said, adding "these arguments must be confirmed so we can use them as a strong weapon."
Ivanov told Russian legislators he would seek a ruling by the United Nations describing the U.S.-led operation as "aggression," a move that would bring about further measures.
Ivanov reiterated that war in Iraq cannot be justified by Resolution 1441.
Ivanov also snubbed Washington, dismissing a worldwide U.S. request to shut down all Iraqi diplomatic missions and expel diplomats.
He said Moscow had not received such a request from Washington, but if it were asked to do so, "it would have no legal force and we would react accordingly."
Russian Finance Minister Alexei Kudrin said he was astonished by a U.S. request to freeze Iraqi bank assets.
"Under our legislation, we can freeze accounts if they are used to finance terrorism or money laundering activities," Kudrin said. "As far as I am aware, there are no facts linking Saddam Hussein's accounts in Russia to such activities."
Meanwhile, Russia prepared to provide emergency aid to an expected flood of refugees from Iraq.
Putin instructed Russian Emergency Situations Minister Sergei Shoigu to send four aircraft with staff and equipment to set up a refugee camp in Kermanshah, near the Iranian-Iraqi border.
Shoigu said the first flight, carrying tents, medicine, power generators, water supplies, food and equipment would fly out to Iran on Friday night. More than 100 Russian specialists would fly out over the weekend to set up a camp to house 5,000 refugees, he said.
Shoigu told Putin that a field hospital would be set up, and a further tent city for refugees could be established should the need arise.
Shoigu said Russia's activities were being coordinated with the United Nations, while an Emergency Ministry official told United Press International that Moscow was ready to discuss with Turkey a plan to set up an additional refugee camp and field hospital there if existing facilities fail to cope with an expected tide of refugees escaping fighting in northern Iraq.
Iran has already asked the international community for aid to house and feed refugees crossing the border from Iraq.