Kenyan police have found leaflets inciting violence being distributed in some areas with less than two weeks to go to general elections.
The police chief said they were intended to spread "fear and panic".
They have been circulating in Kimusu, home to Prime Minister and presidential contender Raila Odinga, and the coastal city of Mombasa.
Following post-election violence five years go, the authorities have been trying to crack down on hate speech.
Hate leaflets, as they are called, were widely distributed after the disputed December 2007 elections. More than 1,000 people were killed in the six weeks of unrest which also forced some 300,000 people from their homes.
Eight candidates are standing for president on 4 March, but Mr Odinga and Deputy Prime Minister Uhuru Kenyatta are considered the two frontrunners.
Mr Kenyatta's candidacy has been controversial as he and his running mate, William Ruto, have been charged with crimes against humanity at the International Criminal Court (ICC) over allegations of fuelling violence in the wake of the last election.
Police Inspector General David Kimaiyo said the leaflets found in Kisumu, a city in western Kenya, were inciting Luo residents to chase away people from the Kikuyu and Kalenjin communities, who traditionally support Mr Kenyatta and Mr Ruto.
Officers were investigating where the leaflets were printed, how they were distributed and who the authors were, he said.
"We are therefore passing a strong message to all those who may want to cause unnecessary fear and panic among members of the public that the long arm of the law will soon catch up with them," he said.
Correspondents say Mombasa, where a secessionist group operates, is often tense in the run-up to elections because of some accusations that the government is marginalising indigenous communities.
The police chief assured the public that special security teams had been sent to areas identified as potential hotspots ahead of the elections when MPs and senators, county governors and members of the newly formed county assembly will also be chosen.
A number of politicians and musicians have appeared in court in the past year on charges of propagating hate speech.
Mr Uhuru and Mr Ruto - rivals in December 2007 poll - are due to go on trial in April in The Hague.