KAMPALA, Uganda (Dow Jones)--The Ugandan army evicted hundreds of immigrant families from communally owned land in the oil-rich Bulisa district over the weekend in a bid to diffuse tensions with locals, officials told Dow Jones Newswires Monday.

Zulu Ganyana, the western Uganda police spokeswoman, said that evictions were carried out following a court ruling last week which nullified the claims of immigrant pastoralists on hundreds of hectares of the land in the oil-rich rift valley.

"The court ruled that the pastoralists were occupying the land illegally," she said, adding that at least 400 people were affected on Sunday.

However, Mukasa Lugalambi, the lawyer representing the evicted families told Dow Jones Newswires separately the army had acted unlawfully in enforcing the evictions because court orders are supposed to be enforced by bailiffs.

"The government's interest in this land is oil, they are not doing this for any tribe, and that's why they are involving the army," he said, adding that he was preparing to file a fresh suit in the Ugandan high court Monday challenging the eviction.

According to Lugalambi, Court threw out the earlier suit on technical grounds after a preliminary objection from the attorney general.

The Uganda police arrested Grace Baroroza, the leader of the affected families, Monday after a group of families attempted to resist eviction. Baroroza told Dow Jones Newswires from the Bulisa police station that she would mobilize her fellow ethnic Banyarwanda tribe not to vote for incumbent President Yoweri Museveni in the forthcoming polls.

"We bought this land but government continues to harass us, they should know that we have the numbers to frustrate government in next year's election," she said.

Tensions between the pastoralists and local Bagungu tribes have been mounting and in 2008, there were several clashes between opposing tribes over the hitherto communally owned land. The pastoralists started migrating into the area around 2006 and acquired title deeds over 1,000 hectares of communally owned land after allegedly buying the said land from local communities.

According to Lugalambi, the entire land in dispute including that without title deeds measures around 8 square miles around block 2, where U.K.-based Tullow Oil PLC (TLW.LN), the operator of the block, is preparing to develop the Kasemene oil field in the fourth quarter of 2011.

Activists say the pastoralists had been aided by some government officials in acquiring the land, the value of which has been rising since the discovery of commercial oil reserves in 2006.

General David Tinyefuza, the Uganda coordinator of the intelligence services, who headed the operation to evict the pastoralists, told reporters Sunday that the army was enforcing a legal court order.

"The evictions are legal and there is nothing wrong with the army getting involved," he said.

Activists have in the past criticized the involvement of the army in the land conflicts in the oil region.

Last month, U.K.-based anti-corruption watchdog, Global Witness, criticized the involvement of the army and Uganda's first family in the oil sector, saying that there is conflict of interest and personalization of oil exploration activities in the country.

Lieutenant Colonel Muhoozi Keinerugaba, the son of the Ugandan president, is the overall commander of the elite Special Forces unit, which is in charge of the security of the oil wells, while General Salim Saleh, the president's brother, owns Saracen security group, which provides private security services to oil exploration companies operating in the country.

Uganda has been discovered at least 15 oil fields in three blocks in the oil region and the country is expected to produce at least 200,000 barrels of oil a day by 2016, according to Tullow.

Discovered reserves so far are estimated at 2.5 billion barrels, according to Tullow.