(Updates at 1150 GMT)
By Alexander Marrow
Oct 2 (Reuters) - The rouble slumped past 99 against the dollar to a near seven-week low on Monday, having now lost support of a favourable month-end tax period and remaining under pressure from Russia's shrinking current account surplus.
The Russian currency tumbled past 100 to the dollar in mid-August, forcing the central bank into an emergency 350-basis-point rate hike and leading authorities to discuss the possibility of reintroducing controls to buttress the currency.
At 1150 GMT, the rouble was 0.8% weaker against the dollar at 98.78, earlier hitting 99.1225, its weakest point since Aug. 15.
It had lost 0.6% to trade at 103.94 versus the euro and shed 0.4% against the yuan to 13.55 .
The yield on Russia's benchmark 10-year OFZ treasury bond reached a more than 18-month high of 13.08%. Bond yields move inversely to their price.
"Along with government debt, pressure has increased on the rouble, which this week is likely to again storm the 100 mark to the dollar, and if it sticks around that, then another wave of accelerating price growth could follow," said CentroCreditBank economist Evgeny Suvorov.
"The central bank needs to move the rate to 15%, but there are still four weeks before the board of directors (meeting). And panic in the market can start at any moment..."
Stubborn inflationary pressure will force Russia's central bank into at least one more rate hike this year, a Reuters poll showed last week, while persistent rouble weakness is among the factors limiting Russia's long-term growth prospects.
Analysts expect the central bank to hike rates to 14% at its Oct. 27 meeting and for double-digit rates to remain until 2025.
The rouble has charted a turbulent course since Russia invaded Ukraine, slumping to a record low of 120 against the dollar in March last year before recovering to a more than seven-year high a few months later, supported by capital controls and surging export revenues.
The rouble has now lost the support of month-end tax payments that usually see exporters convert foreign currency revenues to pay local liabilities.
Brent crude oil, a global benchmark for Russia's main export, was up 0.6% at $92.76 a barrel.
Russian stock indexes were mixed.
The dollar-denominated RTS index was down 0.1% at 1,006.2 points. The rouble-based MOEX Russian index was 0.7% higher at 3.155.2 points.
(Reporting by Alexander Marrow, Editing by Louise Heavens, Kirsten Donovan)