* Police were pursuing cattle rustlers in remote area
* Clashes over water, grazing land part of long dispute
* Fighting heightens tensions ahead of March elections (Adds details)
NAIROBI, Nov 12 (Reuters) - Armed cattle raiders killed at least 32 Kenyan police officers when they ambushed them in the remote northern county of Samburu on Saturday, a government official said on Monday, in the latest fighting between rival tribes in a dispute over land.
Officials had previously put the death toll at 12 and local media has reported at least 40 deaths.
They said raiders from the ethnic Turkana community who had stolen cattle from members of the Samburu community killed police who were pursuing them.
Cattle rustling and clashes over grazing and farming land are relatively common between communities in arid areas of east Africa and often escalate into revenge attacks.
Osman Warfa, provincial commissioner for the vast Rift Valley province, said the attack was carried out using machine-guns, anti-personnel bombs and rocket-propelled grenades.
"We have recovered more bodies, we now have 32 in total. They were ambushed by attackers bearing sophisticated weapons, including machine guns," Warfa told Reuters.
Warfa said authorities were searching for more bodies.
The Turkana and Samburu tribes frequently raid cattle from each other and fight over grazing land and watering points.
Samburu county has a national game reserve and neighbouring Turkana county is where British explorer Tullow Oil struck the country's first promising oil find earlier this year.
In September, more than 100 people were shot, hacked and burnt to death by armed raiders in the coastal county of Tana River, creating security concerns ahead of a presidential election scheduled for March next year. (Reporting by James Macharia; Editing by Yara Bayoumy)