MOSCOW (AFP) - Russia said on Friday that Organisation for Security and Cooperation in Europe (OSCE) observers who were barred from Crimea had failed to obtain "official invitations" from the Crimean authorities.

The OSCE tried to enter Crimea "bypassing the principle of consensus that is fundamental to the OSCE, without considering the opinions and recommendations of the Russian side, without waiting for official invitations from the Crimean side", the ministry said after the organisation reported that gunmen halted its team of 40 observers.

Two buses carrying OSCE observers trying to enter Crimea turned back on Friday after being blocked by armed men at a checkpoint, an AFP reporter said.

Two sources within the mission said the team of 47 military and civilian observers was returning to the Ukrainian city of Kherson where they had spent the night after being similarly blocked on Thursday.

Meanwhile, the International Monetary Fund (IMF) said on Friday it viewed the new government in Ukraine as committed to undertaking needed reforms in exchange for aid.

IMF European Department Director Reza Moghadam said after talks with top leaders that he was "positively impressed" with their "determination, sense of responsibility and commitment to an agenda of economic reform and transparency".