UPDATE 2-Russia c.bank buys dlrs to stop rouble appreciation

(Adds rouble closing, dealers, background)

By Yelena Fabrichnaya and Andrei Ostroukh

MOSCOW, April 25 (Reuters) - Russia's central bank has bought about $20 billion on the forex market this month to prevent the rouble from appreciating against the dual currency basket, First Deputy Chairman Alexei Ulyukayev said on Friday.

"In April we bought about $20 billion. This decision was intended to prevent the rouble's appreciation," Ulyukayev told the parliament.

Dealers said Friday's trade volumes at Moscow's MICEX exchange reached $10.3 billion, with the central bank purchasing about $6 billion.

The rouble opened at 29.53 against the dual currency basket, made of 0.55 dollars and 0.45 euros, way below 29.61, which is seen by the market as the central bank's bid level. The rouble then bounced back to the bid level after interventions.

"Markets are expecting the rouble to appreciate. We saw something like that in the past when suspicions grew that the central bank allow the rouble to strengthen against the basket," said Unicredit currency dealer Alexei Zaitsev.

On Thursday, Ulyukayev said the central bank was ready to tighten monetary policy because foreign capital inflows have picked up again and inflation accelerated to 14 percent in April.

Ulyukayev, who chairs the Bank of Russia's monetary policy committee, said the bank may soon raise interest rates but did not rule out the use of rouble appreciation or an increase in the amount of capital banks have to set aside.