BG Group (>> BG Group plc), Royal Dutch Shell and BP (>> BP plc) were all up between 0.7 and 1.6 percent at 1544 GMT, helping the benchmark FTSE 100 index reverse earlier losses to reach 6,648.72 points, a one-day gain of 0.2 percent.

"Energy shares undid some of the recent declines, surging to the top of the main index as oil prices saw a big short squeeze," said CMC analyst Jasper Lawler.

The mining index <.FTNMX1770> remained in negative territory, down 0.2 percent as copper prices were on track for their biggest weekly loss since September. Miners Rio Tinto (>> Rio Tinto plc), BHP Billiton (>> BHP Billiton plc) and Fresnillo (>> Fresnillo Plc) dropped between 0.1 and 0.8 percent.

"With global growth expectations being reduced, commodity prices will stay under pressure and mining and energy stocks will likely continue to weaken," said John B. Smith, senior fund manager at Brown Shipley.

"The FTSE 100 has had a rally of over 550 points since its low on Oct. 16. In the short term it looks overbought and will probably weaken. I doubt that the index can sustain its rise above 6,500 points."

Aggreko (>> Aggreko plc), the world's biggest temporary power provider, rose 3.3 percent after saying that trading since its interim results in August had been in line with expectations. Underlying group revenue in the third quarter was 6 percent ahead of last year, it said.

British engineering company IMI (>> IMI plc) reversed early losses to rise 1.1 percent after reporting a revenue drop of 6 percent for the four months to the end of October and saying it would acquire German valve maker Bopp & Reuther Holding GmbH for an enterprise value of 152.6 million euros (121 million pounds).

Mid-cap Premier Farnell (>> Premier Farnell plc), a distributor of small electronics and electronic parts, slipped 9.5 percent after warning softer trading conditions in Asia and Europe would leave full-year operating margins slightly below prior year levels.

(Reporting by Atul Prakash and Lionel Laurent; Editing by Catherine Evans)

By Atul Prakash and Lionel Laurent