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By Duncan Miriri and Joseph Sudah

NAIROBI, Nov 23 (Reuters) - Kenya's President Mwai Kibaki has closed a gap with main challenger Raila Odinga and is now running neck-and-neck with him ahead of next month's elections, a poll showed on Friday as fears of a bloody campaign grew.

The latest Steadman survey gave Odinga 43.6 percent to Kibaki's 43.3 percent. Its last poll two weeks ago showed Odinga with 45 percent and the 76-year-old incumbent with 41 percent.

Since then, the often aloof Kibaki has stepped up his appearances in towns and villages across the country. He has even curtailed an official visit to Uganda for the Commonwealth summit to return to the campaign trail.

Some 14 million Kenyans are eligible to vote in presidential and parliamentary elections on Dec. 27. East Africa's biggest economy is traditionally viewed as an oasis of political stability in a volatile region blighted by hunger and disease.

But most Kenyans are braced for violent skirmishes in a tribally tinged race shaping up to be the closest ever.

Police Commissioner Hussein Ali warned politicians against fuelling poll violence after weapons, including clubs, machetes, and bows and arrows, were found in a government car assigned to Raphael Wanjala, an assistant minister.

"I wish to caution politicians and their supporters against attempting to prevent their competitors from presenting their nomination papers by engaging in hooliganism or even abducting their opponents," Ali told a news conference.

"These are very serious offences, some of which attract capital punishment. Anyone who incites violence or targets other candidates must be prepared to face the full might of the law."

Police have asked Wanjala to make a statement on Monday at Criminal Investigation Department headquarters.

Local media said 30 machetes, 20 clubs, 30 dual-edged blades called "Somali swords", 20 bows and 50 arrows were found in the vehicle on Thursday.

"It is all propaganda, I have no knowledge of such weaponry," the Standard newspaper quoted Wanjala as saying.

The arms discovery and reports that youths had been buying huge quantities of machetes from the Nakumatt chain of supermarkets prompted it to limit the sales of garden tools and kitchen utensils that could be used as weapons.

Items such as machetes would be limited to one per customer, a staff member told Reuters. Nakumatt confirmed that it was limiting sales "of domestic items that can be used as offensive weapons".

"We are working closely with the administration and all other security agents to ensure that the safety of all Kenyans is not compromised," Nakumatt Operations Director Thiagarajan Ramamurthy said.

Previous election campaigns in Kenya have been plagued by violence between rival supporters.

Clashes broke out in an election dry run last week with party primaries marred by fighting as crowds set ballot boxes on fire and stoned party officials. (Additional reporting by George Obulutsa and Wangui Kanina in Nairobi, and Antony Gitonga in Naivasha; Writing by Katie Nguyen; Editing by Bryson Hull and Giles Elgood)

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