More than one billion Muslims mark the start of Ramadan on Friday - their holiest month of the year, devoted to prayer, fasting and charity.
But for a small minority, it is also regarded as an auspicious time to escalate violence in the name of jihad.
As a result, experts expect a surge in terrorism attacks during Ramadan, when most Muslims fast from sunrise to sunset in a spiritual exercise that teaches discipline, self-restraint and generosity.
This week, in the run-up to Ramadan, hundreds of Muslims were murdered in Iraq, Afghanistan, Chechnya, Yemen and Somalia.
Seven massive car bombs exploded in Iraq on Wednesday, killing 96 people and injuring 536; yesterday four suicide bombers attacked police posts in Chechnya, just days after a bomb outside a police station in neighbouring Ingushetia killed 25 people and injured 160. Fierce fighting also exploded in Somalia on Friday, killing 22 people, as Islamist rebels launched a Ramadan offensive against African Union peacekeepers in Mogadishu.
"The month of Ramadan has a special status as the month of religious spirituality and devotion. However, in Muslim tradition it is also perceived as a month of jihad, a month in which Allah grants military victories to his believers," says a report by the Washington-based Middle East Media Research Institute (MEMRI).
"It was during Ramadan that Muslims triumphed in many battles throughout the history of jihad for the sake of Allah -- among them the battle of Badr in 624, the conquest of Mecca in 630 and of Andalusia in 711, the battle of Al-Zallaqa (in Andalusia) in 1086, the battle of Ein Jalut in 1260, as well as the 1973 [Yom Kippur War with Israel]."
"Given the historic religious and military significance of Ramadan, Islamist groups, as well as some mainstream Arab organizations, escalate incitement to terrorism during this period," it adds.
In the past, radical Islamists escalated conflicts in Algeria, Afghanistan, Chechnya, Bosnia and Iraq during Ramadan.
On Saturday, Islamist websites are filled with rumours of a new Ramadan message from Osama bin Laden. In the past, al-Qaeda called for Ramadan terror campaigns "to come closer to Allah through the blood of infidels."
This week, Maulana Noor Muhammad, a spokesman for the Pakistani religious organization Jamiat Ulema-e-Islam, told the Urdu-language newspaper Roznama Dunya the Prophet Muhammad regularly undertook battles during Ramadan.
"In such pious times, participate in jihad and continue the support to the mujahideen," he said. "Nowadays, infidel forces want to destroy Islam and the Koranic orders. The fight [against the infidels] is not the responsibility of Taliban and Arab mujahedeen alone; rather it is the responsibility of the entire Ummah [Muslim world].''
In a similar vein, Muslim Khan, a spokesman for the Taliban in Pakistan's Swat Valley, warned his group is preparing a Ramadan offensive.
"The Taliban will intensify attacks," he said. "It won't be long until they gain control of entire Swat Valley. We have a large number of suicide bombers and now is the time to use them."
Last year, 10 days before Ramadan ended, terrorists demolished the Marriott Hotel in Islamabad in a suicide bombing that killed 40 people.
Potential terror attacks are widespread. Police in Saudi Arabia say they broke-up an al-Qaeda cell and arrested 43 Saudis and one foreigner. They seized explosives, machineguns and bomb detonators.
Police in neighbouring Kuwait have also arrested six suspected terrorists, who they say planned to attack Camp Arifjan, home to 15,000 U.S. troops.
Manmohan Singh, India's Prime Minister, says security forces are on the alert for another terror attack by the Pakistani group Lashkar-e-Taiba. He said he has "credible information of ongoing plans of terrorist groups in Pakistan to carry out fresh attacks." Nine months ago, Pakistani gunmen staged a commando-style raid on Mumbai that killed 166 people.
Many Muslims reject radical Islamists and condemn using Ramadan to justify violence.
"Ramadan is about returning to the fountain of truth and drinking from it as deeply as possible," Muqtedar Khan, director of Islamic studies at the University of Delaware, writes. "Unfortunately, for some Muslims, murder and mayhem rather than prayer and fasting have become a way to celebrate Ramadan."
"One cannot imagine to what extent the minds and the hearts of these people have become poisoned, that in the month of Ramadan, when even frowning is undesirable, they chose to murder and maim indiscriminately," he said.
This week, Bangladesh announced it is launching a public awareness campaign during Ramadan to counter calls for violent jihad.
"Teachers of schools, colleges and madrasas and Imams of mosques will campaign against militancy at their respective workplaces across the country," said Shamsul Haque Tuku, state minister for home affairs.
Police in Indonesia, the world's largest Muslim state, will also monitor religious sermons during Ramadan to discourage militancy.
"Police will follow, monitor, record, and if there are any that relate to provocative efforts we will certainly take action," police spokesman Nanan Soekarna said.