RBS bailout, Santander up pace of bank shake-up

* UK pays 15 bln stg for 58 pct Royal Bank Scotland stake

* Commerzbank accelerates Dresdner takeover at cut price

* Santander has full take-up for 7.2 bln euro rights issue

(Adds details of Citigroup, Bank of America and JPMorgan, updates shares)

By Steve Slater

LONDON (Reuters) - Britain's government bought a majority stake in one of the country's biggest banks and Germany's Commerzbank (CBKG.DE) accelerated its takeover of a rival as the shake-up of European banks gathered pace with help from taxpayers and shareholders.

Britain's move was the latest attempt by countries around the world to shore up ailing banks amid a global credit crisis and give them a more solid footing for looming recession.

Shareholders in Royal Bank of Scotland (RBS.L) shunned its share offer, leaving the government to take a 58 percent stake for 15 billion pounds ($23 billion).

In contrast, Spain's Santander (SAN.MC) said investors had signed up for all of its 7.2 billion euro ($9.3 billion) rights issue, which will beef up its capital ratios.

Commerzbank, which has taken 8.2 billion euros from the German government to prop up its flagging finances, cheered investors by saying its purchase price of Dresdner Bank would be 4.7 billion euros less than first envisaged in August and is speeding up the deal.

Insurer Allianz (ALVG.DE), which is selling Dresdner and will get an 18 percent stake in the enlarged Commerzbank, said the takeover could go ahead six to nine months ahead of plan.

"In the current situation on the financial markets, an accelerated takeover of Dresdner by Commerzbank is to the advantage of all parties," said Allianz Chief Executive Michael Diekmann. [nLR119230]

Commerzbank shares surged by as much as 19 percent on the news and ended up 4.9 percent and Allianz jumped 9 percent.

The DJ Stoxx Europe bank sector .SX7P ended up 1.2 percent to 169.07 points.

The index has tumbled over 60 percent this year and investors in many banks have suffered big dilution from fundraisings, but those banks that raised cash should now be well positioned for the downturn, some investors said.

"The dilution has happened and now the banks are well capitalised, they can cope with the bad debts that are inevitably coming, and now people can look at the underlying businesses," said Alan Beaney at Principal Investment Management, which holds shares in most UK banks.