European stock markets struggled Thursday as investors paused for breath, while bitcoin spiked to a dizzying record above $15,000 on frenzied speculative buying, dealers said.

Frankfurt and Paris stocks crept higher in late morning deals but London turned flat on the stronger pound.

However investor focus was on bitcoin, which is not traded on traditional currency markets and hit a fresh high at $15,242.99, according to Bloomberg News.

The controversial virtual unit has soared more than 50 percent in just one week, but analysts warn that the snowballing rally could melt in the run-up to Christmas.