The blue-chip FTSE 100 index, which had fallen in the last three sessions, closed up by 1.11 points - flat in percentage terms - at 6,830.11 points.

A 2.4 percent fall in ARM was one of the biggest drags on the FTSE 100, after investors gave a cautious welcome to a new launch of products from technology company Apple, which is one of ARM's main customers.

The FTSE has lost ground since the start of the week following polls showing a rise in support for the "Yes" campaign that wants Scotland to break away from the UK. Scotland will vote in a referendum on Sept. 18.

The FTSE's meagre 1.1 percent gain since the start of 2014 has underperformed slightly bigger gains of 3.4 percent on France's CAC and 1.4 percent on Germany's DAX.

Analysts said jitters about next week's Scottish referendum, which recent polls suggest is now too close to call, continued to dampen investor sentiment.

"A lot of people are worried about it. I'd be surprised if the Scottish 'Yes' vote goes through but I'd rather stay out of the market then get caught out by a surprise result," said MB Capital trading director Marcus Bullus, who added he was buying U.S. stocks and gold instead of the FTSE.

Terry Torrison, managing director at Monaco-based McLaren Securities, backed Bullus' view that the Scots would choose to vote in favour of staying in the UK next week.

Yet many felt it was now too risky to buy the FTSE.

"I would not buy the FTSE right now. The scenario is still not clear, but I might buy it in the 6,700-6,800 point range," said ActivTrades' senior market analyst Carlo Alberto de Casa.

(Additional reporting by Atul Prakash; Editing by Catherine Evans)

By Sudip Kar-Gupta