diff --git a/src/amoc_controller.erl b/src/amoc_controller.erl
index 3b300467..29b724d9 100644
--- a/src/amoc_controller.erl
+++ b/src/amoc_controller.erl
@@ -298,11 +298,12 @@ handle_start_user(#state{create_users = [], tref = TRef} = State) ->
     State#state{tref = maybe_stop_timer(TRef)}.
 
 -spec handle_start_all_users(state()) -> state().
-handle_start_all_users(#state{create_users = []} = State) ->
-    handle_start_user(State);
-handle_start_all_users(State) ->
-    NewState = handle_start_user(State),
-    handle_start_all_users(NewState).
+handle_start_all_users(#state{create_users   = AllUsers,
+                              scenario       = Scenario,
+                              scenario_state = ScenarioState,
+                              tref = TRef} = State) ->
+    amoc_users_sup_sup:start_children(Scenario, AllUsers, ScenarioState),
+    State#state{create_users = [], tref = maybe_stop_timer(TRef)}.
 
 %% ------------------------------------------------------------------
 %% helpers
diff --git a/src/users/amoc_users_sup.erl b/src/users/amoc_users_sup.erl
index 5adae83a..9f5d67be 100644
--- a/src/users/amoc_users_sup.erl
+++ b/src/users/amoc_users_sup.erl
@@ -49,10 +49,18 @@ handle_cast({start_child, Scenario, Id, ScenarioState}, #state{tid = Tid} = Stat
     case amoc_user:start_link(Scenario, Id, ScenarioState) of
         {ok, Pid} ->
             handle_up_user(Tid, Pid, Id),
-            {noreply, State#state{}};
+            {noreply, State};
         _ ->
             {noreply, State}
     end;
+handle_cast({start_children, Scenario, Ids, ScenarioState}, #state{tid = Tid} = State) ->
+    [ case amoc_user:start_link(Scenario, Id, ScenarioState) of
+          {ok, Pid} ->
+              handle_up_user(Tid, Pid, Id);
+          _ ->
+              ok
+      end || Id <- Ids],
+    {noreply, State};
 handle_cast({stop_child, ForceRemove}, #state{tid = Tid} = State) ->
     Pids = case ets:match_object(Tid, '$1', 1) of
                {[{Pid, _Id}], _} -> [Pid];
diff --git a/src/users/amoc_users_sup_sup.erl b/src/users/amoc_users_sup_sup.erl
index 58158916..ba0808a8 100644
--- a/src/users/amoc_users_sup_sup.erl
+++ b/src/users/amoc_users_sup_sup.erl
@@ -9,7 +9,7 @@
 
 %% API
 -export([init_storage/0, incr_no_of_users/0, decr_no_of_users/0, count_no_of_users/0,
-         start_child/3, stop_children/2, terminate_all_children/0]).
+         start_child/3, start_children/3, stop_children/2, terminate_all_children/0]).
 
 -record(storage, {
           user_count :: atomics:atomics_ref(),
@@ -66,6 +66,17 @@ start_child(Scenario, Id, ScenarioState) ->
     Sup = get_sup_for_user_id(Id),
     gen_server:cast(Sup, {start_child, Scenario, Id, ScenarioState}).
 
+-spec start_children(amoc:scenario(), [amoc_scenario:user_id()], any()) -> ok.
+start_children(Scenario, UserIds, ScenarioState) ->
+    KeyFun = fun(UserId) ->
+                     get_sup_for_user_id(UserId)
+             end,
+    Assignments = maps:groups_from_list(KeyFun, UserIds),
+    CastFun = fun (Sup, Users) ->
+                      gen_server:cast(Sup, {start_children, Scenario, Users, ScenarioState})
+              end,
+    maps:foreach(CastFun, Assignments).
+
 -spec stop_children(non_neg_integer(), boolean()) -> non_neg_integer().
 stop_children(Count, Force) ->
     TotalCount = count_no_of_users(),