President Kibaki appears to be resisting attempts to reduce his powers

The students are angry at the murder of university lecturer Crispin Odhiambo Mbai, who was shot dead by unknown gunmen at his home on Sunday afternoon.

Police intercepted them before they could reach the Bomas of Kenya on the outskirts of the capital, Nairobi.

The academic chaired a key committee at the talks looking into the controversial issue of reducing the president's powers.

This debate has caused a sharp rift within the ruling coalition and there have been accusations from delegates and students that the lecturer may have been assassinated.

Police said they had no evidence to suggest that the motive for the killing was political.

But the atmosphere at the talks was reported to be very tense on Monday.

"It [the killing] has poisoned an already poisoned atmosphere... I don't think it is a good environment for this constitution to be revised," delegate Kathurima M'Inoti told AP news agency.

Broken deal

.A row has been brewing for some time at the conference over the creation of a prime ministerial post.

Raila's party is insisting a premier's post is created

According to a pre-election agreement between the parties that form the ruling National Rainbow Coalition (Narc), the post of executive prime minister was to have been created and allocated to Raila Odinga's Liberal Democratic Party (LDP).

But President Kibaki now insists that Kenya cannot have two centres of power, infuriating Mr Odinga, who is the public works and roads minister.

Mr Odinga's followers played a major role in President Kibaki's overwhelming victory in the 2002 general elections.

Mr Odinga has described Mbai's killing as an "assassination", saying that nothing was stolen from the house.

Police have launched an investigation and appealed for public witnesses.

Strains within the ruling alliance have become more evident since the death of Vice-President Wamalwa, with heavy political lobbying to fill the vacant post.