MANAMA, Bahrain – Riot police firing tear gas and wielding clubs stormed a landmark square occupied by anti-government protesters early today, driving out demonstrators and destroying a makeshift encampment that had become the hub for demands to bring sweeping political changes to the kingdom.

The main opposition group Al Wefaq said at least two people were killed in the pre-dawn assault on Pearl Square, which was littered with flattened tents, trampled banners and broken glass. There was no official word on deaths or injuries, but hospitals reported dozens of people being brought in with wounds and respiratory problems from the tear gas.

ABC News said its correspondent, Miguel Marquez, was caught in the crowd and beaten by men with billy clubs, although he was not badly injured.

Hours after police retook control of the plaza, the tiny island nation was in lockdown mode. Tanks and armored personnel carriers were seen in some areas – the first sign of military involvement in the crisis. Police checkpoints were set up along main roadways and armed patrols moved through neighborhoods in an apparent attempt to thwart any mass gatherings.

Barbed wire was put up around Pearl Square and a message from the Interior Ministry declared the protest camp “illegal.” The air still carried the smell of tear gas more than four hours after the assault.

The blow by authorities marked a dramatic shift in tactics. It appeared Bahrain’s leaders had sought to rein in security forces after clashes Monday that left at least two people dead and brought sharp criticism from Western allies – including the U.S. – which operates its main naval base in the Gulf from Bahrain.

Police held back Wednesday as tens of thousands of protesters crowded into the seaside square, dominated by a 300-foot monument to Bahrain’s history as a pearl diving center.

The Egypt-inspired protests began Monday as a cry for the country’s Sunni monarchy to loosen its grip, including hand-picking most top government posts, and open more opportunities for the country’s majority Shiites.