The average-weighted dollar exchange rate at today's special session on US currency grew by RUR0.02 to 31.41 RUR/USD. Specialists of commercial banks attribute this weakening of the ruble to the Central Bank's activities. According to experts, the Central Bank was purchasing US currency at 31.40 RUR/USD at the UTS, which was RUR0.01 higher than the official dollar rate for March 18. The Central Bank's ruble intervention was pretty active. Some analysts say that one of the lots of dollars purchased by the Central Bank at this morning's session, amounted to $40m. At the same time, the Bank was preventing the growth in the weighted average dollar rate above the 31.41 RUR/USD level. According to specialists, the Central Bank could have been selling dollars at this level. Nevertheless, the volume of purchased US currency prevailed over the amount of sold dollars at the UTS. Analysts think that the Central Bank bought about $150m at the special session today.