Story highlights The protest was organized by an anti-government group

The group's leader calls off the rally after police step in

Police defend their use of tear gas

More than 130 people are detained

The leader of a Thai anti-government party called off a rally Saturday after police used tear gas to disperse more than 50,000 people who showed up in Bangkok to take part, the state-run Thai news agency reported.

Gen. Boonlert Kaewprasit also said he will not head any anti-government rally in the future and will not enter politics, the MCOT news agency said.

Boonlert said he called off Saturday's rally by the Pitak Siam group to save protesters' lives. Just before the rally was to begin Saturday morning at Bangkok's Royal Plaza, MCOT said, police used tear gas to disperse the crowd.

When the crowd tried to break through a concrete barrier to get to the rally site, police in riot gear with shields used tear gas again to push protesters back.

More than 130 people were reportedly detained by police and 10 people, including four police officers, were reportedly hurt, mostly from tear gas, MCOT said.

Pitak Siam, whose name means "Protecting Siam," wants to overthrow the government of Prime Minister Yingluck Shinawatra, who has been in office since last year, MCOT reported.

The group is separate from the so-called Yellow Shirts, a group that formed to oust Yingluck's brother, Thaksin Shinawatra, from power. Thaksin was exiled after a military coup in 2006.

Boonlert said use of the tear gas was "improper" because the protesters were unarmed, but police defended the move, saying it was the best way to avoid clashes.

Police Gen. Adul Saengsingkaew said officers first used the tear gas because protesters tried to enter a restricted area near the Royal Plaza.

The protesters, he said in a statement, "proceeded to cut through seven layers of barbed wire, pushing back the officials as well as ramming a large-sized vehicle into the officers. As such, it was necessary for the officers to carry out the procedures in negotiating, issuing a warning and using tear gas which is considered to be in accordance to what was agreed, the law and rules of engagement."