MANAMA, Bahrain: Tens of thousands of Bahraini protesters encircled one of the royal family's palaces Saturday, shouting calls for political freedom and the king's ouster a day after a similar march triggered a violent response from security forces. There was no repeat of the violent scenes from a day earlier when police backed by pro-government mobs drove crowds back from a different palace by firing rubber bullets and tear gas in a melee that injured dozens, according to witness accounts. In contrast, Saturday's demonstration — which coincided with a visit by US Defense Secretary Robert Gates — was allowed to ring the palace with police deployed only inside its premises. Gates said Bahrain and other Arab governments facing uprisings need to move quickly toward democratic reforms or risk giving regional rival Iran a chance to exploit the instability. Gates said Saturday he believes leaders in Bahrain are serious about addressing grievances. “I told them that in this instance, time is not our friend” in light of Iran's interest in capitalizing on the unrest, the Pentagon chief said in an interview after meetings in Manama, the capital. “We have no evidence that suggested that Iran started any of these popular revolutions or demonstrations across the region, but there is clear evidence that as the process is protracted — particularly in Bahrain — that the Iranians are looking for ways to exploit it and create problems,” Gates told reporters on his flight home from the Mideast. Gates offered no examples of that. But a senior defense official traveling with Gates said US intelligence has evidence that Iran is working to persuade some opposition figures in Bahrain to reject the government's offer to begin a political dialogue on how to address a range of grievances. Gates was in Bahrain to encourage dialogue between the protesters and the ruling family. Bahrain holds particular importance to Washington as the host of the US Navy's 5th Fleet, the main American military counterweight to Iran's efforts to expand its armed forces and reach into the Gulf.