TOKYO (AFX-ASIA) - The yen weakened to beyond the 123 yen level after the Bank of Japan voted to boost its current account target to 6 trln yen from 5 trln previously, dealers said. The central bank also raised monthly purchases of long-term government bonds to 600 bln yen from the previous 400 bln yen following the two-day policy board meeting. Nomura Securities Co Ltd foreign exchange manager Takashi Toyohara said the market showed an "immediate and knee-jerk reaction" to the announcement by the central bank. He, however, questioned the sustanability of the dollar's rebound, citing the underlying concerns over the future trend of the US economy, adding that "the latest depreciation of the dollar was not based on Japanese leads, but was brought about by US leads". "If the dollar fails to recover the 125 yen level following today's leads, the unit may be pushed lower again and test the 120 yen level." Dealers said investors' focus is likely to return to the weakness of the US economy and the performance of US stockmarkets once the initial reaction to the BoJ's decision runs out of steam. Aozora Bank foreign exchange deputy manager Kazuhiro Nishina said the dollar will be exposed to downside risk, rather than extending its rebound of late, citing receding hopes for any quick recovery in the US. "Technically speaking, unless the dollar recovers the 124 yen level, it will not be able to gain any sustained upward momentum," he said. "The dollar, if there is any fresh negative lead, may be pushed to test the recent low of 121.30 yen."