There is a sect called MAHDAWIS (followers of mahdi). According to them Syed Mohammed Jonpuri who was born in India in 900 Hijra is the real Mahdi and, anyone who does not believe in him is a Kafir. For this reason Mahdawis don't pray with other Muslims. What is the truth in the context of Qur'an and Sunnah?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. The persons, who claim to be Mahdi, are numerous. All of them proclaim to be the real al-Mahdi including Mohammad from Jonpour (India). Their false claims are refuted by texts of Shari'a (Qur'an and Hadith) proving he has not yet appeared. He will come in the last period just before the descent of Christ. The followers of Mohammad Jonpuri are among the deviant sects who turned away from the true Muslim community.
Please refer to the Fatwa82108.
Allah knows best.