Front month November Brent slumped 82 cents by 0915 GMT to $21.26, nearly $3 below 33-month highs struck just last week. October gas oil was also on the slide, down $6.50 a tonne at $173.50 a tonne. "It's still really negative.

Sell stops are being triggered and people are baling out all over the place," said one dealer. Brent struck an early low of $21.25, some 83 cents down as Brent extended its string of losses into a fifth straight day. Falls have accelerated through this week as a survey showed OPEC compliance with output curbs slackened in September. This has encouraged heavy profit-taking from the speculative buyers who fuelled oil's rise from sub-$10 lows in February. "It's onwards and downwards. If OPEC has shown a small amount of leakage then the speculators are going to worry that it's going to get evenworse in October and November," said a trader. "But it's natural long liquidation, not a big change in fundamentals. There have been some massive long positions sitting in there for months and if they are selling out at these numbers then they're making pots of money." The falls have come even though OPEC reaffirmed at its September conference a deal with some non-OPEC producers to keep to current output limits until at least March next year.

Traders have become edgy since Reuters survey of OPEC and industry officials and consultants published on Wednesday showed the export cartel raised wellhead output in September by 180,000 barrels per day (bpd).

The survey showed adherence by OPEC members taking part in supply restrictions, excluding Iraq, fell to 81 percent in September from 84 percent in August.

Long positions have also been unsettled at the prospect of a meeting next month between the oil ministers of Saudi Arabia, Venezuela and Mexico - the architects of the deal to cut back production untilMarch next year. The Mexican minister, Luis Tellez, said on Thursday that the meeting would discuss post-March production policy, but added there was a "clear intent" to keep oil prices at recent levels. Traders will be keeping a close eye on the CFTC Commitment of Traders report out after the close of trade on Friday to see how much speculative length the recent sell-off has taken out of the market.