Kagyu Monlam ("moen" in Tibetan means aspiration, and "lam" means path) is a prayer for peace in the world. The Karmapa had earlier explained that the Kagyu Moenlam prayer is an avenue through which, in times of dire need, love and compassion can be made to spread like a great ripple outwards from Bodh Gaya.
Hundreds of Buddhists, including monks and lamas from different countries, are attending the Kagyu Moenlam prayer led by Karmapa Ugyen Trinley Dorje.
"The Karmapa started prayers seeking world peace," a police official said.
Gaya senior superintendent of police Nishant Kumar Tiwari said special security arrangements have been made for the Karmapa and for Buddhists attending the prayer in view of the perception of a terrorist threat.
The Karmapa will stay in Bodh Gaya till the completion of prayers next week.
Last week, intelligence agencies alerted Bihar Police of a possible threat to Buddhist tourists likely to visit Bodh Gaya this winter.
The serial bomb blasts at the Mahabodhi Temple in Bodh Gaya July 7 this year shocked the state government, local residents and tourists.
Ten bombs exploded at or in the vicinity of the temple and two Buddhist monks were injured. Three live bombs were recovered and defused that day.
After the serial blasts, the security at the temple was beefed up.
The Mahabodhi Temple - a Unesco World Heritage Site - in Bodh Gaya, about 110 km from the state capital, is where the Buddha, born in neighbouring Nepal, attained enlightenment around 2,550 years ago.
The Karmapa has been staying in India as a guest since the year 2000 when he fled the Tsurfu Monastery in Tibet by giving the slip to Chinese authorities. After his escape, he took shelter with the spiritual head of Tibetan Buddhists, the Dalai Lama, at Dharamsala in Himachal Pradesh.