Two bits of evidence indicating that Osama bin Laden is alive have surfaced in the last 10 days.

Last week the al Qaeda leader threatened to kill any captured Americans if the United States executed Khalid Sheik Mohammed, the self-professed mastermind of the September 11 attacks, or other al Qaeda suspects.

The warning was contained in a 74-second audiotape played on Al-Jazeera television, when bin Laden explicitly mentioned Mohammed, who was captured in Pakistan in 2003. He is the most senior al Qaeda operative in US custody and is detained at the US naval base at Guantanamo Bay, Cuba.

The other strand of evidence was reported by Newsweek magazine this week, citing a secret FBI recording of captured Al Qaeda operative Raja Lharsib Khan discussing his relationship with other terrorist factions.

Khan was reportedly in contact near the Afghanistan border with Ilyas Kashmiri, the head of a Sunni extremist group linked to Al Qaeda.

Khan was updated about bin Laden after meeting with Kashmiri. The Al Qaeda head was "commanding everythings [sic]," Khan said Kashmiri had told him, according to an FBI affidavit.

Security experts say Khan's claims are difficult to verify, although there is said to be evidence he has been in the region where talks with Kashmiri could occur.

In the videotaped threat, bin Laden warned Americans could suffer if Mohammed was given the death penalty.

"The White House has expressed its desire to execute them. The day America makes that decision will be the day it has issued a death sentence for any one of you that is taken captive," Bin Laden said, addressing Americans.

Diplomatic and media sources have traced the dispatch of bin Laden's recent audio statement to Bangalore in India. According to a senior journalist the audio message was sent via a courier from India.

Area specialists confirm at least one more such audio tape released in 2006 was also handed over to a courier in Hyderabad India who delivered it to a contact in an Arab TV office in the Middle East.

Al Qaeda is not known to have any Americans captive but the Haqqani group - the Pakistan-based Taleban faction closest to al Qaeda - is holding American soldier Private first class Bowe Bergdahl who was captured in eastern Afghanistan in June 2009.

It released a video of him in December.

Bin Laden also said President Barack Obama was following in the footsteps of his predecessor George W. Bush by escalating the war in Afghanistan, being "unjust" to al Qaeda prisoners and supporting Israel in its occupation of Palestinian land.

"The politicians of the White House were and still are wronging us, especially by supporting Israel and occupying our land in Palestine. They think that America, behind oceans, is safe from the wrath of the oppressed, until the reaction was loud and strong in your homeland," he said of the September 11 attacks. "Equal treatment is only fair. War is a back-and-forth."