The European Central Bank shook up currency markets in London trading hours Friday, as a fresh bout of bond-buying pushed the euro higher and bolstered rallies in other risky currencies from around the world.

The day had started quietly, with key currencies holding steady ahead of crucial US employment data due at 1330 GMT. But the tone changed as traders said that the ECB was buying Irish, Greek and Portuguese bonds, in its second march into the market in two days.