* Police, military troops on trail of raiders
* Ambush highlighted police weaknesses
* Residents fear reprisal attacks
By Humphrey Malalo and Noor Ali
NAIROBI, Nov 14 (Reuters) - Kenya on Wednesday charged five regional officials with the murder of 32 Kenyan police officers killed by armed cattle raiders in an ambush at the weekend, described as the worst attack on the country's police.
The junior officials, who oversee a cluster of villages in the northwestern region, pleaded not guilty after they were arrested early on Wednesday.
Police and troops, backed by military helicopters, launched an offensive against the raiders suspected to be from the ethnic Turkana community who had stolen cattle from the Samburu tribe.
Clashes over cattle, land and water are common among Kenya's fringe tribes, but many in the east African country were shocked by extent of the violence and the kind of weapons used.
The raiders used machine guns and rocket propelled grenades to kill the officers in a military-style ambush in the remote northwestern territory. Some unconfirmed media reports said up to 42 bodies had been recovered in the rugged Suguta valley.
Osman Warfa, provincial commissioner of the vast Rift Valley province, said the five junior regional officials planned the attack. The five were also charged with livestock theft and were being held in custody to assist with investigations.
"We obtained credible information after investigating that implicated the five," Warfa told Reuters.
"They planned the raid, kept the stolen animals and instructed the raiders to kill the officers."
The attack has highlighted how ill-equipped Kenya's police force is, at a time when they are facing new challenges.
There is pressure to improve the force ahead of elections next March - the first since a disputed election in 2007 fuelled ethnic slaughter that killed more than 1,200 people and forced about 300,000 from their homes.
Police Commissioner Mathew Iteere has called for armoured vehicles for his forces and a tactical rethink in the wake of the massacre.
Kenya shares porous borders with South Sudan, Ethiopia's Somali region and Somalia - territories awash with weapons and arms smugglers after decades of conflict.
Military helicopters swooped low over the site of the ambush at Suguta Valley in north west Kenya, tracking a convoy of trucks ferrying police officers and paramilitary units, residents at the nearby town of Baragoi said.
Kenya's President Mwai Kibaki had on Tuesday night ordered military troops to join in a crackdown on the attackers.
"Baragoi is like Kismayu or Somalia today," said Raphael Lekulkulai, a shopkeeper from the Samburu tribe in Baragoi said, referring to a city in Somalia that African peacekeepers recently entered to drive out al Qaeda-linked militants.
"Our town is like a military camp, helicopters are flying, taking-off, landing. The number of police (and) paramilitary in military jungle uniforms is almost more or equal to the local population," he said.
Thousands of people, mostly Turkana, started fleeing Suguta Valley on Tuesday fearing reprisals after security forces blamed members of the ethnic group for the killings.
"We are all afraid, tension is high. Almost all Turkanas who have stayed here for decades have left. I am planning to leave this place as soon as possible," James Loche, a Turkana elder in Baragoi said. (Writing by Yara Bayoumy; editing by James Macharia and Keiron Henderson)