The FTSE 100 index was up 0.2%, while the FTSE 250 midcap index added 0.1% by 0709 GMT.

Oil majors Shell and BP rose slightly as tensions in the Middle East escalated after a media report said that U.S. President Donald Trump had approved military strikes on Friday against Iran.

IQE Plc, which makes semiconductor wafers for chips, slumped 37.2% and was on course for its worst day on record after warning annual revenue would be lower-than-expected because of U.S. restrictions on China's Huawei, which is affecting orders.