By Sara Sjolin, MarketWatch

LONDON (MarketWatch)--The U.K.'s benchmark stock index dropped on Monday, with mining firms adding pressure and Vodafone Group PLC on the decline after a new partnership agreement.

The FTSE 100 index fell 0.3% to 6,310.26, partly erasing a 1% gain from last week.

Shares of Vodafone Group PLC (>> Vodafone Group plc) lost 0.5%, as the wireless-telecom firm announced the creation of a strategic five-year partnership with BAE Systems PLC. (>> BAE Systems PLC (ADR)) The deal aims to provide business with advanced communications-security products. Shares of BAE Systems fell 0.6%.

Shares of Anglo American lost 2.3%, after media reports said five workers were shot at an Anglo American Platinum Ltd.'s South Africa mine. Anglo American holds a majority stake in Anglo American Platinum.

Other mining firms also declined, even as most metals prices were on the rise. Shares of Antofagasta PLC lost 1.9%, Vedanta Resources PLC fell 1.8% and Rio Tinto PLC (>> Rio Tinto plc) gave up 1.1%.

Oil prices were lower, adding pressure on U.K. oil firms. Shares of BP PLC (>> BP plc) lost 0.7% and BG Group PLC fell 0.3%.

International Consolidated Airlines Group SA (>> International Consolidated Airlines Grp) fell 1.3%, as its Iberia airline said it would cancel 236 flights during the first of the 15 days its workers are planning to strike.

Banks were mostly lower. Shares of Royal Bank of Scotland Group PLC (>> Royal Bank of Scotland Group plc) fell 1.5%, Barclays PLC (>> Barclays PLC) slipped 0.5% and HSBC Holdings PLC (>> HSBC Holdings plc) nudged 0.2% lower.

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