Much of Spain was brought to a halt by a general strike on Thursday, but the bond market vigilantes are also striking, by avoiding the country’s debt.

Yields on Spanish 10-year bonds rose sharply in March, overtaking the rate on sovereign debt in Italy — another troubled peripheral euro zone economy — for the first time since August.

Rates for Italy and Portugal — which have at different times taken the leading role in the euro zone debt drama — have fallen in the wake of the European Central Bank’s decision to flood the euro zone banking system with hundreds of billions of euros of cash on the final day of February; a move repeating its successful December initiative. Although this injection of liquidity has moderated fears that a credit crunch could hit other risky government bond markets, concerns about Spain have risen, as the bond vigilantes have protested against the country’s fiscal woes by selling their Spanish debt or even shorting the market. Why is this?