|Street battles have flared up almost every day for the past month, particularly in predominantly Shia villages [Reuters]
Bahrain has deployed thousands of security forces to confront anti-government protesters ahead of the first anniversary of the start of a Shia-led uprising that seeks to loosen the ruling Sunni dynasty's monopoly on power.
Opposition groups urged demonstrators to stream towards an empty area dubbed "Freedom Square" outside the capital, Manama.
Some activists seek to occupy the site before Tuesday's anniversary of the start of the wave of protests, and turn it into a new semi-permanent hub for the uprising.
The central Manama roundabout was the opposition's headquarters during the first weeks of the Shia majority's campaign against the Sunni monarchy.
Authorities imposed martial law after security forces stormed the protesters' encampment at the landmark square, and later tore down the pearl sculpture that marked the site.
The now heavily guarded square holds great symbolic value for Bahrain's opposition movement, and protesters have repeatedly tried to retake it. But the capital has largely been off limits to demonstrators since March.
|Critics say neither Bahrain nor Washington has done enough to foster democratic reforms in the Gulf nation
Street battles between security forces and protesters still flare up almost every day in the predominantly Shia villages around the capital.
Bahrain's ruling Sunni monarchy has said it would not tolerate a rise in protests to mark the anniversary. Sporadic clashes occurred on Sunday with police firing tear gas.
The island's King Hamad bin Isa Al Khalifa said last year's events were regrettable, although he downplayed the severity of the threat the protests had posed to the 200-year-old-rule of the Sunni dynasty.
The king says that a massive opposition movement does not really exist in the country.
"I regret the events of the past year,'' he told the German weekly Der Spiegel in an interview that was published on Sunday.
"But there is no opposition in Bahrain, not in the sense of a united bloc. Such a thing is not in our constitution. There are just people with different views, and that is good."
Villages under 'siege'
Shias account for about 70 per cent of Bahrain's population of some 525,000 people, but say they have faced decades of discrimination, such as being denied access to senior political and security posts.
Bahrain's Sunni rulers have taken steps on reforms, including relinquishing more powers to parliament. In an announcement early on Monday, Bahrain's king named a Shia, Sadok bin Abdulkarim al-Shehabi, as health minister.
The health position is significant because Bahrain's main hospital figured prominently during the early weeks of the uprising with authorities claiming medical staff aided demonstrators. Dozens of doctors and nurses have been put on trial.
The government, however, has so far refused to make the far-reaching changes the protesters and the main Shia group, Al Wefaq, the country's largest opposition party, have demanded.
These include ending the monarchy's ability to select the government and set all-important state policies.
Al Wefaq criticised the authorities for imposing "a siege" on the villages around Manama ahead of the first anniversary of Bahrain's "revolution".
Its statement on Sunday said police stormed houses and fired tear gas indiscriminately in densely populated civilian areas. There were no reports of injuries, but Al Wefaq said several people were detained.
At least 40 people have been killed during months of unprecedented political unrest in Bahrain, the Gulf country hardest hit by unrest during last year's Arab Spring protests.
Neighbouring Saudi Arabia and other Sunni-ruled Gulf states dispatched troops to Bahrain in March to help quell the protests.
In another tightening of policies, the official Bahrain News Agency said the kingdom would demand prior visa approval for many nations that had been allowed to obtain entry stamps upon arrival, including the US and other Western countries.
The decision follows the deportation on Sunday of two American activists accused of joining protests after entering on tourist visas.