Radical Iraqi cleric Moqtada al-Sadr returned to the holy city of Najaf from Iran on Wednesday, a source within his office told AFP. "Moqtada al-Sadr arrived at his home in Al-Hannana in Najaf this afternoon," said the source, speaking on condition of anonymity. "We don't know if this visit will be for a long time or not." Sadr returned to Iran, where he spent four years of self-imposed exile, on January 20 after having spent two weeks in Iraq. While in Iraq last month, the firebrand cleric called on his supporters to resist the US "occupation" by all means. He had left Iraq at the end of 2006 or early in 2007, according to US and Iraqi officials, and had reportedly been pursuing religious studies in the Iranian holy city of Qom. The controversial Sadr gained widespread popularity among Shiites in the months after the 2003 US-led invasion, and his Mahdi Army militia later battled American and Iraqi government forces in several bloody confrontations. But in August 2008, Sadr suspended the activities of the Mahdi Army, which once numbered in the tens of thousands, after major US and Iraqi assaults on its strongholds in Baghdad and southern Iraq in the spring.