FTSE hit by weaker oil but records strongest month for two years

* Blue (OTC BB: BUES - news) -chip FTSE 100 ends 0.5 pct lower

* Oil companies fall on weak U.S (Other OTC: UBGXF - news) . data

* IAG results disappoint investors

* RBS (LSE: RBS.L - news) down on Q3 loss, faces litigation costs

By Kit Rees

LONDON, Oct (HKSE: 3366-OL.HK - news) 30 (Reuters) - Disappointing company results depressed UK shares on Friday, and energy firms fell as the price of crude oil retreated after weak U.S. economic growth data.

Among leading decliners, Royal Bank of Scotland shares slipped 1 percent after the bank posted a third-quarter loss and warned that future costs relating to litigation and past misconduct might be substantially higher than expected.

The blue-chip FTSE 100 index ended 0.5 percent lower at 6,361.09 points, although it registered its biggest monthly gains since July 2013.

"I'm still of the theory that this is a bear market rally," CMC Markets market analyst, Jasper Lawler, said.

"I think no one ... can confidently say that we are going to be breaking out higher into the next leg of the bull market right now, and with the uncertainty, and the fact that we've already had a good, strong move higher, leads me to think that maybe we could be about to turn down."

Oil companies fell after the price of oil slipped following disappointing U.S. economic growth figures, with the UK Oil & Gas index dropping 1.1 percent.

Shares (Berlin: DI6.BE - news) in airline IAG fell 2.5 percent, to be the top decliner in the FTSE 100, after its profit guidance disappointed investors.

"This reversion looks like little more than profit-taking off the back of the good news, but as has been noted this is a cyclical industry and how much more upside is left does present a reason to be cautious," Trustnet Direct market analyst Tony Cross wrote in a note.

Among mid-cap companies, drug developer Vectura Group (LSE: VEC.L - news) rose 6.7 percent after the U.S. Food and Drug Administration cleared treatments for chronic obstructive pulmonary disease. (Additional reporting by Atul Prakash; Editing by Richard Balmforth)