UN chief Ban Ki-moon has called on all sides in Kenya to stop the violence that has wracked the country since December's disputed presidential poll.
"Look beyond the party lines. Look towards the future," he urged.
As he spoke, news came through that eight people had been poisoned and hacked to death in an apparent revenge attack for the killing of an MP.
Mr Ban met opposition leader Raila Odinga in Kenya, after seeing President Mwai Kibaki on Thursday in Ethiopia.
Mediation talks between the government and opposition have resumed.
The latest violence was said to be in response to the killing of opposition MP David Too, who was shot dead by a policeman in the western town of Eldoret on Thursday.
Police said at least eight people had been killed and dozens of houses torched in fresh fighting in the western Nyanza province.
Six people were said to have been hacked to death and another two killed by poisoned arrows.
The police say the MP was caught up in a domestic dispute but the opposition says he was assassinated.
At least three opposition supporters were also shot dead by police in overnight clashes.
The BBC's Wanyama Chebusiri in Eldoret says there were running battles overnight between opposition supporters and the police.
Thirteen people are in hospital with gun shot wounds, he says.
France has called on the UN Security Council to help stop the violence.
Foreign Minister Bernard Kouchner expressed fear that the country was being allowed to slide into a "deadly ethnic conflict."
More than 850 people have died in political and ethnic violence since the 27 December presidential elections, which the opposition says were rigged.
Correspondents say the purpose of the UN secretary general's visit is to offer support to his predecessor, Kofi Annan, who is mediating talks between the two sides, and to be briefed on the humanitarian crisis.
There has been fresh violence in the Rift Valley
"I'm reasonably encouraged by the commitment and the willingness of all the political leaders as well the community leaders who are now looking at the possibility of resolving this issue though dialogue and peaceful means," Mr Ban told reporters, AFP news agency quotes him as saying.
"You have lost already too much in terms of national image... You lost many tourists, this is a very unfortunate situation for a country which has been enjoying freedom and security and stability," he said.
In a statement issued from Paris, Mr Kouchner called on the UN Security Council to act.
"In the name of its duty to protect, it must urgently come to the aid of Kenya's population," he said in a statement.
"Barbaric acts are being committed, civilian populations are being killed in atrocious ways, with women and children raped."
Mr Too was the second MP to be killed this week and his shooting led to the talks to be postponed until Friday.
As well as the trouble in Eldoret, police fired teargas to disperse protesters in the town of Kisumu, and in the MP's home town of Kericho, buildings were set alight.
Our correspondent says there is now a heavy security presence in Eldoret and the town remains tense.
Kericho is reported to be deserted with paramilitary police on the streets and shops and banks closed, he says.
A small community of honey hunters who live in the mountains overlooking the Rift Valley has also been caught up in the violence.
Some Ogiek houses have been burnt down and many have gone into hiding the forests where they lack food.
"When they are burning Ogiek houses they are saying it is because you voted for the Orange Democratic Movement," Kiplangat Cherugot, who works for a non-governmental organisation in the area, told the BBC's Network Africa programme.