MOSCOW, June 28 (Reuters) - The Russian rouble weakened

against the dollar after exporters completed their forex sales

to meet Friday's monthly tax payment deadline.

Traders said Thursday's announcement by the central bank

that it would reduce its daily foreign currency sales in the

second half of the year - separate from the operations it

conducts on behalf of the finance ministry - was also a factor

weighing against the rouble.

On the interbank market, where liquidity can be low as major

Russian banks that have been sanctioned cannot participate, the

rouble traded 1.5% lower at 86.30 to the dollar by 0756

GMT.

The average dollar-rouble mixed composite rate, calculated

by LSEG and based on data from international brokers and

counterparties, stood at 86.24.

The central bank's official dollar-rouble rate was set at

84.96 for June 28, calculated on the basis of OTC trading.

Sanctions on Moscow Exchange and its clearing

agent, the National Clearing Centre (NCC), have led to a range

of varying prices and spreads after it halted exchange trading

in the dollar and euro this month. Trade moved to the

over-the-counter (OTC) market on June 14.

Russia's central bank said on Thursday it would sell 8.4

billion roubles ($97.4 million) worth of foreign currency per

day in the second half of the year, down from 11.8 billion

roubles in the first half.

The central bank's operations are conducted on the domestic

forex market in Chinese yuan, and are related to the

replenishment and spending of money from the state's rainy day

National Welfare Fund.

The bank's own forex operations are separate from those it

conducts on behalf of the finance ministry, for which in the

current month it is buying the equivalent of 3.7 billion roubles

a day of foreign currency.

On Friday the rouble was trading at 11.70 to the yuan, down

1.6%.

Brent crude oil, a global benchmark for Russia's

main export, was up 0.7% at $86.96 a barrel. Traders said the

firm oil price and expectations that the Russian central bank

would increase its key rate at its July meeting would lend

support to the rouble.