A relative of a victim breaks down during a visit to Ground Zero in New York. (Reuters)

Singapore, Sept. 11 (Reuters): Two middle-aged Arabs walking down a rock-strewn hillside leaning on canes may appear harmless. When the pair are Osama bin Laden and his deputy, Ayman al-Zawahri, the stroll is no less than a renewed declaration of war.

The two top leaders of the al Qaida network that is blamed for the September 11, 2001, strikes on New York and Washington appear in a rare tape obtained by al Jazeera descending a rocky mountainside as they steadied themselves with walking sticks, automatic rifles slung over their shoulders.

Accompanying the video was a recorded call to arms from the Saudi-born bin Laden and a declaration from his Egyptian aide urging fighters to turn Iraq into a graveyard for US troops.

The video, breathing al Qaida defiance and taunting US President George W. Bush and his war on terror, is the first sighting of bin Laden since December 2001 and while apparently filmed in April or May shows he remains alive, analysts said.

“The timing is obviously significant and is designed to do several things,” said David Wright-Neville, former terrorism adviser to Australia’s office of National Assessments, equivalent of the US National Security Agency.

“First, they want to continue to foster the fear of the unknown. One of the principal objectives of terrorism is to prey on that fear,” said Wright-Neville, now at the Monash Global Terrorism Research Unit in Melbourne, Australia. “They have assessed, quite correctly, that there is an ongoing fear of terrorism and they want to perpetuate and feed that,” he said.

The al Qaida leaders, who walk beside white spring flowers and pick their way among tufts of long verdant grass in what could be mountains in northern Pakistan or Afghanistan, take a great risk in showing themselves and giving a hint to US hunters as to their whereabouts, say counter-terrorist experts.

But if their aim is to maintain their mystique, to propagate their message and to prove to their followers that they remain a force with which the US must reckon, then they need to make such risky — if rare — appearances, they say.

Forty-seven-year-old bin Laden, believed to have been wounded in the left shoulder or arm during the Tora Bora campaign in eastern Afghanistan in late 2001, has clearly healed.

“He is looking in pretty good fettle... alive and well,” said Peter Bergen, author of Holy War, Inc: Inside the Secret World of Osama bin Laden.

While the release of a tape to coincide with the September 11 anniversary surprised few security experts who had expected an audio message at the very least, the appearance of bin Laden astonished some.

“The thing that surprised was the video,” said Bergen. “The reason they wouldn’t want to release this is because they do not want to reveal their whereabouts. “The catch 22 is that to remain effective they have to keep putting out these tapes,” he said. “On the other hand, it’s the most obvious way to lead back to them. It’s a risk.”

In his last appearance on video in December 2001, bin Laden appeared grey-faced and tired, unable to move his left side. In this video he appears spry and moves with ease, bending down to sling a Kalashnikov rifle over his shoulder before making his way, sure-footed, down the hillside with al-Zawahri.

“This feeds the image of Osama bin Laden as the indestructible warrior for Islam,” said Wright-Neville. “He depends on his charismatic status among disenfranchised Muslims around the world and he needs to send a message that he is well.”

Experts said it was impossible to say whether the audiotapes from bin Laden and al-Zawahri, 52, contained some coded message, but most agreed that it sufficed to issue the call to“devour” US forces in Iraq and to urge Pakistanis to rise up to defeat US ally, Pakistani President Pervez Musharraf.

Neither could a message be ruled out. “It sounds like an indication to operatives to carry out whatever plans had been put into effect,” said Andrew Tan, security expert at the Institute of Defence and Strategic Studies in Singapore.