Dubai's main stock market plunged for a second consecutive day Tuesday and an international ratings agency again downgraded six state-linked companies as fresh concerns surfaced about the troubled Arab boomtown's debt woes.

The twin blows came as the sheikdom's finance chief raised new questions about the pace of restructuring at government-owned Dubai World, the debt-saddled conglomerate now at the heart of the emirate's credit mess.

Abdul Rahman al-Saleh, the finance department's director-general, said restructuring the sprawling conglomerate _ which has operations the world over ranging from ports to real estate to tourism _ would take more than six months. He also said the group's property arm Nakheel had received government aid, but that the cash injection was distinct from any state guarantee of debt now owed to banks worldwide.

Lenders until two weeks ago had assumed Dubai's many state-affiliated companies had implicit government backing _ an assumption Dubai officials have since debunked.

"We've taken the message on board," Philipp Lotter, Moody's senior vice president, said in an interview after the credit agency cut ratings on government-linked companies it covers. "The consequences of this precedent have become very clear in Dubai. Companies are now viewed on a very much stand-alone basis."

Days earlier, Standard & Poor's also cut to junk status several of the same companies.

Dubai shocked markets a day before the U.S. Thanksgiving holiday with the announcement that Dubai World would seek a "standstill" _ effectively a delay _ on repaying some of its debts until at least May. The company later said it wanted to restructure roughly $26 billion of its debts, and Dubai officials have indicated that an asset sale was possible.

The news has hammered local markets.

Shares on the Dubai Financial Market tumbled 6.1 percent to close at 1,638.05. An accelerated slide since October has now left prices where they were at the end of 2008, effectively erasing a year's worth of gains.

The bourse in Abu Dhabi _ the neighboring oil-rich emirate that is home to the United Arab Emirates' federal government _ dropped by over 3.3 percent. Most other Gulf markets also fell.

Al-Saleh told the Saudi-owned satellite channel al-Arabiya that the government has previously given Nakheel, Dubai World's property developer subsidiary, $2.45 billion to pay its bills. He did not say when the funds were pumped into the struggling company. Spokesmen for the department could not be reached.