The leader of the Zapatista rebels in southern Mexico, Subcomandante Marcos, announced Sunday that he was stepping down as head of the 20-year-old group.

Marcos claimed that he was leaving due to internal changes and would no longer serve as a voice for the movement which is seeking to garner better rights for indigenous groups in the state of Chiapas.

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As mysterious and enigmatic as Subcomandante Marcos may seem, he has been identified by authorities as Rafael Sebastián Guillén a former philosophy professor who taught at Mexico City's National Autonomous University.

The militant leader also quelled rumors that he was resigning because he is unwell, claiming that the opposition chose to spread the misinformation in order to discredit him and his movement and make them appear weak.

"I declare that the one known as Insurgent Subcomandante Marcos no longer exists," Guillén said in a statement released on a Zapatista website.

The announcement was made only a day after Guillén made his first appearance in public in over five years. The Subcomandante was seen in Chiapas attending a ceremony for a fallen comrade and wearing his trademark mask and smoking his familiar pipe.

The Zapatista movement began in 1994 and gains its title from the 1910 Mexican revolutionary hero Emiliano Zapata.

After the first emergence of the rebellious group, a 12-day conflict ensued with the government and came to an end only after federal authorities signed a pact with the Zapatistas.

However, none of the Zapatista group's demands, which were entailed in the peace treaty, were met; driving the movement to create their own autonomous justice, health and education systems in several communities.

According to reports, Subcomandante Marcos will be replaced by a man called Moises who was promoted to Subcomandante in February.

The impact of Guillén's decision on the movement as a whole remains to be seen.