By Atul Prakash

LONDON (Reuters) – Britain’s top share index hit a five-week low on Friday and headed for its biggest weekly drop in eight months, with growth-driven stocks losing ground on tensions before a referendum in Ukraine’s Crimea region.

The blue-chip FTSE 100 index was down 0.3 percent at 6,537.36 points by 1130 GMT, taking the week’s total losses to 2.6 percent, the biggest decline since June last year. The index has fallen 5 percent since a high in late February.

The fund management, retail and mining sectors, all highly sensitive to economic conditions, came under pressure as investors looked to cut exposure to riskier assets heading into the weekend, when Ukrainians in Crimea vote on whether to join Russia. Moscow said it would veto a U.S.-drafted UN resolution to declare the referendum illegal.

“The market is spooked due to the prospect of more sanctions against Russia as an awful lot of money comes to the market from some very rich Russian investors. The FTSE was touching new highs anyway and Sunday’s referendum has become a perfect excuse to take some money off the table,” David Battersby, investment manager at Redmayne-Bentley, said.

“Until the Ukraine crisis is sorted out, which could drag on for a while, the market does have the potential to move down even further. But I am not talking about a massive leg downwards. In the worst case scenario, the FTSE 100 could fall up to 6,400, at which point it will become relatively cheaper.”

The UK mining index fell 0.7 percent to become the top sectoral decliner, led lower by a 1.2 percent drop in global miner Rio Tinto.

The UK’s second-largest independent asset manager Aberdeen Asset Management fell 2.5 percent, the top decliner on the FTSE 100 index, while building supplies group CRH was down 2.2 percent.

After falling below its 50-day and 100-day moving averages this week, the FTSE 100 fell below its 200-day moving average and a 61.8 percent Fibonacci retracement of a rally from February 4 to 24 on Thursday, pointing to a bearish trend.

“We’ve broken through 50-day and 200-day moving averages by a chunk and that’s no real surprise,” Alastair McCaig, analyst at IG, said.

“Every noise I’ve heard suggests that Crimea will vote to join Russia … and while the market is expecting that, it’s the consequences of it that make it more problematic.”

(Additional reporting by Alistair Smout; Editing by Stephen Powell)