Image copyright Reuters Image caption Ayman al-Zawahiri wants al-Qaeda to be the world's foremost jihadist group

Al-Qaeda leader Ayman al-Zawahiri has announced in a videoed message the creation of an Indian branch of his militant group to "raise the flag of jihad" across South Asia.

In the 55-minute video posted online, Zawahiri pledged renewed loyalty to Afghan Taliban leader Mullah Omar.

Correspondents say his stated allegiance is an apparent snub to Islamic State (IS) militants.

IS is challenging al-Qaeda to lead worldwide Islamist militancy.

Announcing the formation of "al-Qaeda in the Indian Subcontinent" using a mixture of his native Arabic and Urdu widely spoken in Pakistan, Zawahiri appeared eager to regain some of the limelight, correspondents say.

"[Al-Qaeda] is an entity that was formed to promulgate the call of the reviving imam, Sheikh Osama Bin Laden. May Allah have mercy upon him," Zawahiri said.

He urged the "umma", or Muslim nation, to "wage jihad against its enemies, to liberate its land, to restore its sovereignty and to revive its caliphate".

Zawahiri said "al-Qaeda in the Indian Subcontinent" would be good news for Muslims in Myanmar (Burma), Bangladesh and in the Indian states of Assam, Gujarat and Jammu and Kashmir, where they would be rescued from injustice and oppression.

Analysis, BBC security correspondent Frank Gardner

Image copyright AP Image caption Zawahiri (right) - photographed here with Osama Bin Laden in 2001 - is eager to carry on the policies of his predecessor

It was always going to be a challenge for Osama Bin Laden's successor to match his iconic status and maintain al-Qaeda as the most powerful jihadist group in the world.

Ayman al-Zawahiri, the nominal leader of al-Qaeda, is a 63-year-old former Egyptian eye surgeon said to be long on words and short on charm.

For over a decade he has dodged drone strikes and hit squads by hiding out in Pakistan and Afghanistan.

But apart from issuing occasionally long-winded treatises and videos, his critics say he has allowed al-Qaeda to wither while Islamic State (IS) has grown into everything al-Qaeda tried - and failed - to be.

While al-Qaeda's remaining leaders hide away in farms and flats in Pakistan, IS has seized and held actual territory.

It has a de facto capital, Raqqa, a disciplined command structure, an estimated $2bn (£1.2bn) war chest.

It has the world's attention and despite its sadistic atrocities, it is enjoying a surge in recruitment that Zawahiri could only dream about.

India's intelligence and security services are studying the announcement by Zawahiri very closely and have also asked their state units to remain vigilant on any possible threat.

A spokesperson for India's ruling Bharatiya Janata Party (BJP) told the Associated Press news agency that the statement was "a matter of serious concern".

"But there is nothing to worry about. We have a strong government at the federal level," the spokesperson said.

Counter-terrorism experts say al-Qaeda's ageing leadership is vying with IS to recruit followers after the success of militants in the Middle East in attracting young followers worldwide by conquering large amounts of territory across Iraq and Syria.

IS leader Abu Bakr al-Baghdadi describes himself as a "caliph" - or head of state - and has called for the support of all Muslims around the world.

The two groups fell out in 2013 over the IS expansion into Syria, where Baghdadi's followers have carried out mass murder, decapitations and crucifixions.

On Wednesday it emerged that Pakistani militants linked to IS have been distributing pamphlets in the north-western city of Peshawar calling on people to support their idea of creating an Islamic caliphate.

Graffiti and car stickers supporting IS have also started appearing in the city and its outskirts, reports the BBC Shahzeb Jillani in Pakistan.

The material, published in the Pashto and Dari languages, urges people to support IS in its fight for a grand Islamic rule.