Kenyan authorities should expand investigations into the alleged roles of four politicians in clashes in the country's southeast which killed 110 people in three weeks, an international human rights group said Thursday

President Mwai Kibaki late Wednesday sacked assistant Livestock Development Minister Dhado Godhana after he was charged in court with inciting the violence.

Kibaki chaired a cabinet meeting Thursday which issued a statement saying that "tough measures" should be used to quell the violence. The police force held a press conference earlier asking for clear directions from the cabinet on what kind of measures they should use so that they are not accused of brutality and prosecuted. Human rights lawyer Harun Ndubi criticized the vague cabinet announcement, saying that it amounts to giving police tacit approval to shoot to kill.

Human Rights watch said its investigations show that three more politicians could be involved in the violence between the semi-nomadic Orma tribe of herders and the Pokomo, who are mostly farmers in the Tana River Delta.

The U.N. and Red Cross say that on the surface the violence appears to be a historical feud over land and water resources, but there are additional contributing factors including the redrawing of political boundaries and next year's general elections.

The violence in August and September was the culmination of smaller-scale attacks, cattle raids and counterattacks since January between the ethnic Pokomo and Orma communities, the Human Rights Watch statement said

Both communities have lost lives and livestock, but police either failed to respond to the attacks or arrested people and then released them without investigations, it said.

"Several politicians or political hopefuls have been linked to the violence in Tana River," said Leslie Lefkow, deputy Africa director at Human Rights Watch. "Ending the political violence in Tana River requires bringing to book those behind the clashes on both sides."

Lefkow said for decades the Kenya police have failed to investigate politicians who may be implicated in serious crimes and if they are ready to do so now, the authorities must be even handed and investigate all sides.

The Kenya Red Cross says that more than 200 people have died in Kenya this year in clashes which fit a pattern of violence before elections in three out of four of Kenya's elections since 1992.

The recent violence in the Tana River Delta as well as intertribal clashes in northern Kenya, which have left 12 dead so far, have raised fears that there would be an explosion of violence as the March 2013 elections draw closer.

Kenya's parliament Wednesday passed a motion urging the government to deploy the military to pacify the two tribes, after nine police officers were killed.

Dunson Mungatana, the Member of Parliament for Garsen, the constituency for Tana River, said that police were overwhelmed by the fighting because the attacks went on despite a dusk to dawn curfew being imposed on Monday.

Another legislator opposed the measure, saying the army is not trained to deal with such domestic disputes and can be brutal to civilians.

Kenya's cabinet did not approve the deployment of the army but additional police officers and said that a commission of inquiry led by a judge should be set up to investigate the cause of the conflict.

The United States has called on all parties throughout Kenya to address grievances and assert their rights through peaceful means, as provided for in the new constitution,

"So that all Kenyans may participate in fair and credible elections in March 2013," the statement issued by the U.S. Department of State said Thursday.