Ugandan soldiers, who are tracking down Lord's Resistance Army (LRA) fugitive leaders

Three Ugandan military helicopters crashed in Kenyan airspace at the weekend on their way to Somalia and bad weather was hampering search and rescue efforts, a Kenyan defence spokesman said on Monday.

A pilot from one of the three helicopters was in touch with authorities, who were searching for the survivors in the Mount Kenya region of central Kenya, reports Reuters.

It was not clear how many people were aboard the Russian-built MI-24 helicopters when they crashed on Sunday or how many had survived. Officials have not said whether the helicopters were brought down or suffered mechanical failure.

"We are waiting for the weather to clear at Mount Kenya so that we can strengthen our efforts for search and rescue," Kenya's Department of Defence spokesman, Bogita Ongeri said.

Ongeri said four Ugandan helicopters left a base in the Ugandan city of Entebbe on Sunday to reinforce African Union peacekeeping forces battling al Shabaab rebels, but only one landed at a Kenyan base in Garissa on the border with Somalia.

Ugandan troops form the backbone of the African Union peacekeeping force (AMISOM) in Somalia. The air force said on August 7 that it was deploying transport and combat helicopters to Somalia to beef up the force.

The African Union force, which also includes Kenyan and Burundian troops, is planning an offensive on Somalia's second biggest city Kismayu, which is a hub for the Islamist militants, before August 20.

Al Shabaab struck the Ugandan capital Kampala in mid-2010 when suicide bombers from the al Qaeda-linked group killed more than 70 people who were watching soccer on television, in revenge for the presence of Ugandan troops in Somalia.