European Central Bank (ECB) president Mario Draghi has said that he will come up with more measures to support the euro "over the coming weeks".

"The euro is irreversible," he said, adding that the high yields on some eurozone government bonds were unacceptable.

He said the ECB may intervene in the bond markets to support struggling nations.

Earlier, the ECB kept the main eurozone interest rate at a record low of 0.75%.

Last week, hopes had been raised of fresh action when Mr Draghi said he would do "whatever it takes" to support the euro.

Spain's borrowing costs are at high levels, prompting speculation that it will need a full bailout.

One commentator told the BBC that it was "crunch time for the euro".

The Spanish government sold 3.1bn euros of debt at an auction earlier on Thursday, but again had to pay more to borrow the money.

The average interest rate on 10-year bonds rose to 6.65% from 6.43% at the last auction on 5 July.

Last week, the yield on Spanish 10-year bonds hit a record high of 7.6% on the secondary market, where bonds sold at previous auctions are bought and sold.

This raised concerns that the country would need a full bailout, beyond the help for its struggling banks that has already been agreed.

Greece, Portugal and the Republic of Ireland all had to seek international bailouts when their borrowing costs reached similar levels.

The ECB, which sets the cost of borrowing for the 17 countries which use the euro, cut its key rate from 1% to 0.75% last month, to try to bring down borrowing costs and stimulate economic activity.