there are still attackers in the deputy president's "expansive" home near the town of Eldoret, some 312 kilometres (200 miles) northwest of the capital Nairobi.

"More security personnel have been deployed and a security operation is ongoing," the officer said, and witnesses reported hearing several gunshots from the compound shortly after reinforcements arrived.

Their accounts differed from a statement issued by Kenya's police hours after the assault, which said someone carrying a machete attacked a police officer guarding the entrance to the residence and then fled into the compound.

"Other officers were quickly mobilised and the intruder was forced to hide at a building that is still under construction next to the gate," Kenya's police chief Joseph Boinnet said in a statement.

The attack occurred despite the round-the-clock presence of guards fromthe GSU's top-notch reconnaissance unit.

A spokesman for Ruto declined to comment but the security official said the deputy president had left the house shortly before the attack to attend rallies alongside President Uhuru Kenyatta, his running mate who faces a tight re-election contest on August 8 against longtime opposition leader Raila Odinga.

- Tensions mounting ahead of vote -

Ruto's home sits in Kenya's western Rift Valley area, the flashpoint for an outbreak of election violence after the disputed 2007 polls that killed 1,100 people and tarnished Kenya's image as a regional beacon of safety and stability.

According to opinion polls, this year's election will be close and tensions have been rising.

Odinga has repeatedly claimed the government is scheming to steal the election, while Kenyatta has accused Odinga of trying to