Special report: Tension escalates in Iraq

   ; BAGHDAD, June 16 (Xinhua) -- A Sunni mosque was destroyed in an explosion Saturday in Iraq's southern city of Basra in the latest apparent retaliation after the minarets of a revered Shiite shrine were blown up.

    Militants blew up the al-Ashrah al-Mubashra mosque in al-Hakimiya district Saturday morning in Basra, the main Shiite city 550 km south of Baghdad, local police said.

    On Friday, another Sunni mosque near Basra, the Talha Bin al-Zubair shrine, was attacked and destroyed. Afterward, Iraqi Prime Minister Nouri al-Maliki ordered an indefinite curfew in Basra.

    Several Sunni mosques have been attacked or burned down since insurgents Wednesday blew up two minarets of the Imam Ali al-Hadi shrine in Samarra City, some 120 north of Baghdad.

    In February 2006, the holy shrine's famous golden dome was destroyed which triggered a wave of retaliatory sectarian violence, pushing the country to a full-scale sectarian clashes.

    The destruction of the remaining minarets raised immediately fears of a new round of tit-for-tat attacks between rival sects.

    The capital of Baghdad is still under curfew on Saturday, which began on Wednesday afternoon and is expected to end on Sunday.

    Meanwhile, U.S. Defense Secretary Robert Gates is on a surprise visit to Baghdad in a new bid to press Iraqi leaders to achieve reconciliation among rival factions.

    Gates, who arrived here late Friday night, met top U.S. commanders for a briefing on the security situation on Saturday morning. He is scheduled to meet with al-Maliki later.

    This is Gate's fourth trip to the country since taking over as U.S. defense chief in December.

    Following the footsteps of U.S. Deputy Secretary of State John Negroponte and U.S. Commander in the Middle East William Fallon, Gates becomes the third senior U.S. official to visit Baghdad this week.