By Alexander Marrow and Elena Fabrichnaya
(Reuters) - The Russian rouble strengthened to 93 against the dollar on Thursday, in a volatile week filled with speculation over how the authorities might stabilise the currency after a 350-basis-point rate hike appeared to have only a limited effect.
The Bank of Russia increased its key rate to 12% on Tuesday, an emergency attempt to halt the rouble's recent slide past the symbolic 100 threshold, but analysts said more measures may be needed to return the rouble to the 80-90 range authorities have deemed acceptable.
By 1005 GMT, the rouble was 1.8% stronger against the dollar at 92.92, earlier clipping a two-week high. It had reached a near 17-month low of 101.75 against the dollar on Monday.
The rouble had gained 2% to trade at 101.07 versus the euro. It had also firmed 1.7% against the yuan to 12.69.
Authorities are discussing bringing back the compulsory sale of foreign currency revenues for exporters, five sources told Reuters. Beyond rate hikes and capital controls, Moscow has some other options, though none particularly favourable.
The Vedomosti daily late on Wednesday reported that mandated FX sales would not be reintroduced for now and that exporters had informally agreed to raise sales.
But a high-level source told Reuters an update was possible "at any moment", saying that the Vedomosti story largely focused on the government's point of view in a broad coalition holding talks.
Another source told Reuters that exporters were being told to sell as much FX as possible and provide weekly updates.
On the 25th anniversary of the rouble's 1998 devaluation, which followed rates of 150% and panic buying in shops, Russian traders were set to gather later on Thursday for 'Dealer's Fest', an event to mark the start of "a new era of the Russian financial market".
The rouble is around 15 times weaker than it was in August 1998, down from 6.3 to the dollar then to 95 now.
The Russian currency should start seeing support from exporters preparing to pay month-end taxes, for which they usually convert FX revenues into roubles.
Brent crude oil, a global benchmark for Russia's main export, was up 0.7% at $84.06 a barrel.
Russian stock indexes were mixed.
The dollar-denominated RTS index was up 1.7% to 1,031.5 points. The rouble-based MOEX Russian index was 0.2% lower at 3,042.9 points.