Accordion ItemCommand event not firing

I have a user control where I am using an Accordion control having the kind of structure as follows. I have a linkbutton control in the HeaderTemplate.

<asp:Accordion ID="Accordion1" runat="server" AutoSize="Fill" Width="800px" 
                                                   FadeTransitions="true" 
                                                    TransitionDuration="250" 
                                                    FramesPerSecond="40" 
                                                    RequireOpenedPane="false" 
                                                    SuppressHeaderPostbacks="true" 
                                                    HeaderCssClass="accordionHeader" 
                                                    ContentCssClass="accordionContent"> 
        <HeaderTemplate> 
            &nbsp;<asp:LinkButton ID="txtArtist" CommandName="Select" Width="100%" runat="server"><%#Eval("Title")%></asp:LinkButton>         
        </HeaderTemplate> 
        <ContentTemplate>         
            <asp:Repeater id="repeaterEstimator" runat="server"> 
                <ItemTemplate></ItemTemplate> 
       </asp:Repeater> 
       </ContentTemplate>         
  </asp:Accordion> 

I want to fire ItemCommand event on clicking the link button and in the code behind run some business logic based on the CommandName.

void Accordion1_ItemCommand(object sender, CommandEventArgs e)
        {

            if (e.CommandName == "Select")
            {
                int index = Accordion1.SelectedIndex;
                if(index>0) {
                //Execute some business logic here
                }
            }
        }

The ItemCommand event is not firing when I click the button.

I am using Ajax Toolkit dll version:3.5.51116.0

Thanks,

Saikat