Bahrain's security forces fired tear gas and rubber bullets Monday at thousands of anti-government protesters heeding calls to unite in a major rally and bring the Arab reform wave to the Gulf for the first time.

The punishing tactics by authorities appeared to foil plans for a mass gathering in Bahrain's capital Manama, but it underscored the sharply rising tensions in the tiny island kingdom — a strategic Western ally and home to the U.S. Navy's 5th Fleet.

At least 25 people were treated for injuries, and one man died after being found on the street with severe head trauma, according to family members.

Riot police — some firing bird shot pellets — moved against marchers trying to reach central Manama in an act that organizers intended as an homage to Egypt's Tahrir Square, the epicenter of the popular revolt that drove Hosni Mubarak from power.

Bahrain's protesters, however, claim they do not seek to overthrow the ruling monarchy but want greater political freedoms and sweeping changes in how the country is run.

Social media sites have been flooded with calls by an array of political youth groups, rights activists and others to join demonstrations on Monday, a symbolic day in Bahrain as the anniversary of the country's 2002 constitution that brought pro-democracy reforms such as an elected parliament.

But opposition groups seek deeper changes from the country's ruling dynasty, including transferring more decision-making powers to the parliament and breaking the monarchy's grip on senior government posts. Bahrain's majority Shiites — about 70 percent of the population — have long complained of systemic discrimination by the Sunni rulers.

The nation — no bigger in area than New York City — is among the most politically volatile in the Gulf. A crackdown on perceived dissidents last year touched off riots and street battles in Shiite areas.

On a highway to the capital, marchers ran for cover under a cloud of tear gas and barrage of bird shot fired by police. By nightfall, police vans and other vehicles blocked main roads into the city, which was largely deserted in many places as businesses closed early in anticipation of possible violence. Malls and other shopping areas were closed.

In the mostly Shiite village of Diraz, police fired rubber bullets and tear gas to halt a march by hundreds of peaceful demonstrators waving Bahraini flags and chanting: "No Shiites, no Sunnis, only Bahrainis."

One woman sat in the road in front of riot squads and demanded freedom for all political prisoners.

Earlier, security forces moved against marchers in the mostly Shiite village of Newidrat in the southwest region. At least several people were injured, said witnesses, who spoke on condition of anonymity because of worries of reprisals from authorities.

On Sunday, security units and protesters clashed in the Shiite village of Karzakan in western Bahrain, injuring several demonstrators and police.

In Manama, security forces were on high alert in anticipation of possible protesters streaming toward the main crossroads in a plan designed to echo Cairo's Tahrir Square.

Bahrain's leaders have responded to the "Day of Rage" calls with concessions aimed at appeasing the protesters.

Government regulators have promised to ease state controls on the media. Last week, King Hamad bin Isa Al Khalifa granted each Bahraini family the equivalent of nearly $2,700. Bahrain lacks the energy riches of most other Gulf nations and cannot afford to match the generous social programs common in the region.

In an open letter to the king, the independent Bahrain Center for Human Rights set high demands for reforms and warned that attempts to crush protests could push the country into "chaos and bloodshed." The list includes dismantling the security forces, prosecution of state officials for abuses and the release of 450 jailed activists, religious leaders and others.

Bahrain's Sunni leaders point to parliamentary elections as a symbol of political openness in the nation of about 525,000 citizens. The 40-seat chamber — one of the few popularly elected bodies in the Gulf — has 18 opposition lawmakers.

But many Sunnis in Bahrain also are highly suspicious of Shiite activists, claiming they seek to undermine the state and have cultural bonds with Shiite heavyweight Iran. An ongoing trial in Bahrain accuses 25 Shiites of plotting against the country's leadership.

In Kuwait, opposition groups had called for an anti-government protest last week, but shifted the date to March 8 after the resignation of the country's scandal-tainted interior minister.