Al-Qaida leader Ayman al-Zawahiri has warned the US of the “gravest consequences” if Boston marathon bomber Dzhokhar Tsarnaev or any other Muslim prisoner is executed.



Tsarnaev, named in Zawahiri’s online video message, was sentenced to death by lethal injection last year for the 2013 bomb attack that killed three people and injured more than 260 others. Tsarnaev committed the bombing with his older brother, Tamerlan, who was killed in a shootout with police in the manhunt that followed it.

“If the US administration kills our brother the hero Dzhokhar Tsarnaev or any Muslim,” Zawahri said in an online video, “[it] will bring America’s nationals the gravest consequences.”



The younger sibling spoke publicly only once since his capture, telling the Boston court that sentenced him: “I am sorry for the lives I have taken, for the suffering that I have caused you for the damage I have done – irreparable damage.”

Zawahri urged Muslims to take captive as many westerners as possible, especially those whose countries had joined the “Crusaders’ Campaign led by the United States”.



The Egyptian-born militant, sitting in front of green drapes, urged sympathizers to hold “crusaders” hostage in order to bargain for Muslim prisoners’ release. He said that western nations “only understand the language of force”.

Zawahiri took command of al-Qaida after Osama bin Laden was killed in 2011, by a US raid in Pakistan. The 64-year-old successor has eluded American strikes in the five years since, but the group’s influence has waned while rivals have gained power around the Middle East. Al-Qaida remains an active presence in Yemen, Pakistan and Libya, but its affiliate in Iraq grew into the terror group Isis as the civil war in neighboring Syria spiraled out of control.



Al-Qaida’s propaganda arm periodically threatens nations with recorded messages and long statements. In January Zawahiri condemned the execution of a Shiite cleric, Nimr al-Nimr, and 46 others by Saudi Arabia. Later that month two men attacked a Shia mosque in the majority Sunni country, though no group claimed credit. The attack resembled those inspired by Isis, whose leader Zawahiri has called a false “caliph of surprises”.

Zawahiri remains wanted by the US and has appeared in dozens of al-Qaida propaganda messages since 2003. In a September message he urged militants to move “the war to the heart of the homes and cities of the crusader west and specifically America”, and again called Isis’s territorial claims illegitimate.

Tsarnaev is being held at a high-security prison in Florence, Colorado, while his attorneys appeal the death sentence. The legal struggle over his ultimate fate could last decades: since 1998, US authorities have executed only three of the 74 people sentenced to death for federal crimes.

Reuters contributed to this report.