Moscow, Apr 7 (IANS/RIA Novosti); Moscow believes the UN is disrupting an investigation into the alleged use of chemical weapons in Syria under pressure from "certain states", the Russian foreign ministry said.

"We cannot but make a conclusion that under the pressure of certain states the UN Secretariat has adopted an unconstructive and inconsistent stance and is basically disrupting the investigation into particular reports of the possible use of chemical weapons in Syria on March 19, which could be verified at this stage," a ministry statement said.

The foreign ministry criticised the UN move as "unacceptable and intolerable" and called on the organisation to act on the principles of "impartiality".

Syria's authorities accused opposition militants of deploying chemical weapons in an attack near the northern city of Aleppo March 19 that state media reports said killed at least 25 people and injured more than 100.

The rebels have denied the allegation and instead accused the Syrian military of launching a Scud missile with a chemical warhead.

UN Secretary General Ban Ki-moon said the UN will open an independent investigation into the alleged chemical weapons attack in Syria as soon as possible.

Russian foreign ministry spokesman Alexander Lukashevich said in a statement that however, later Ban Ki-moon, "under pressure from Western members of the Council", took an "unjustified step" of broadening the mandate of the mission in an effort to set as its task the investigation of all other alleged cases of chemical weapons use in Syria.

Lukashevich described Ban's approach to the issue as "counterproductive", saying there is no information regarding any other incidents of the use of chemical weapons in Syria.