Yemeni tribal chief Sadiq al-Ahmar has emerged as one of the most prominent challengers to the authority of Yemen's president, who is trying to suppress a months-long uprising against his authoritarian rule.
Al-Ahmar is the leader of northern Yemen's Hashid federation, the most powerful tribal organization in an impoverished country where tribal loyalties run deep. Yemeni President Ali Abdullah Saleh's tribe is a part of that federation.
Al-Ahmar had been a member of Saleh's ruling General People's Congress party until February, when the tribal chief resigned to protest a government crackdown on opposition demonstrators demanding the president's ouster.
He joined the protesters in March by calling for Saleh to quit the post he has held for almost 33 years. In a joint statement with prominent clerics, al-Ahmar also held the president responsible for the killings of more than 50 opposition activists by pro-Saleh gunmen at a rally in Sana'a.
The tension between al-Ahmar and Saleh boiled over on May 23, when the tribal chief's fighters began attacking government targets in the capital. Pro-Saleh forces fired on al-Ahmar's Sana'a residence.
Both sides accused each other of starting the fighting, which spread to other parts of the city and killed dozens of tribal and government forces.
Al-Ahmar intensified his verbal attacks on Saleh, calling the president a "liar" who will leave the country "barefoot." Saleh's government has issued arrest warrants for al-Ahmar and his sons, calling them gangsters and accusing them of high treason.
The tribal chief's father, Abdullah bin Hussein al-Ahmar, also led the Hashid federation. He served under Saleh in the powerful political role of parliamentary speaker until he died of cancer in 2007.
Some information for this report was provided by AP, AFP and Reuters.