Concerns over renewed attacks raised in Washington

Threats against America contained in an audio tape indicating strongly it is the voice of al Qaeda leader Osama bin Laden, as well as other intelligence material, have raised concerns in Washington of renewed attacks, prompting the government to take extra precautions, White House spokesman Scott McClellan said.

He gave no details of the precautions and said there were no plans to raise the formal national threat advisory level, which remains at the yellow, or "elevated" level, meaning a significant risk of terrorist attack.

Federal agencies were boosting protection measures and keeping state and local law enforcement agencies informed of intelligence assessments, he said.

At the same time Federal officials played down the significance of a recent FBI warning of possible attacks on hospitals in four cities, saying they were based on dubious information.

"Health care professionals and patients in these cities should feel comfortable going to their hospitals," said Gordon Johndroe, spokesman for the Office of Homeland Security. "The government is assessing the situation but we currently believe it is one of low credibility."

US intelligence agencies have been analysing the recording purported to be of bin Laden since it was broadcast by Qatar's al-Jazeera television channel on Tuesday.

US military and intelligence agencies have been hunting for him, mainly along the Afghanistan-Pakistan border, on the assumption he was alive until proven dead.

The United States has not had solid evidence since December 2001 that he survived the US bombing of Afghanistan aimed at destroying al Qaeda, which was blamed for the September 11, 2001 attacks on America that killed about 3,000 people.

"The bottom line is he's probably alive," the intelligence official said on condition of anonymity.

The voice on the tape praised recent attacks including bombings in Bali, Indonesia, accused the United States and its allies of harming Muslims and threatened: "As you kill, you will be killed."

Senate Democratic Leader Tom Daschle of South Dakota questioned the success of the Bush administration's war on terrorism with bin Laden still on the loose and al Qaeda still a threat to US interests.

"I'm troubled that we haven't found bin Laden in all this time," he said. "It causes many of us to be concerned about whether or not we're winning the war on terror."

The White House's McClellan countered by saying "tremendous progress" had been made in fighting terrorism but it was going to be a long war.

"If Osama bin Laden is alive, we know he's on the run. We have dismantled his terrorist network. And we are going to continue tracking down these trained killers and their leaders and their networks wherever they are and bringing these people to justice," he said.

US officials have said the audiotape may have been released to boost the morale of bin Laden's followers but also could signal new attacks. Bin Laden has released tapes in the past that have been followed by attacks.

An increased level of "chatter," or threats by al Qaeda operatives picked up by intelligence agencies eavesdropping on their communications, has also led to concern that another attack was coming.

The CIA and National Security Agency have been analyzing the Jazeera broadcast. Linguists who are familiar with bin Laden's voice had already determined the recording sounded like the Saudi-born militant, but a technical analysis had so far not been conclusive.

It now appeared the technical analysis will match the conclusion of the linguists that it was indeed bin Laden.

The analysis found indications that the recording, which was not very clear, was made over a telephone - probably a hard line rather than a cellular or satellite phone.

The message could have been taped in one location, then taken to another location and played over the telephone and recorded at the other end in a third location, so there was no indication of where bin Laden might be, a U.S. official said.

Ahmad Muaffaq Zaidan, Jazeera's bureau chief in Pakistan, said the tape was delivered to him by an unidentified man in Islamabad.

"All it tells you is that the guy who handed the tape to somebody was in Pakistan," and offers no indication of where bin Laden might be hiding, a US official said.