For an arbitrary set X and an equivalence relation µ on X, denote by P µ (X) the semigroup of partial transformations α on X such that xµ ⊆ x(ker(α)) for every x ∈ dom(α), and the image of α is a partial transversal of µ. Every transversal K of µ defines a subgroup G = G K of P µ (X).We study subsemigroups G, U of P µ (X) generated by G ∪ U , where U is any set of elements of P µ (X) of rank less than |X/µ|. We show that each G, U is a regular semigroup, describe Green's relations and ideals in G, U , and determine when G, U is an inverse semigroup and when it is a completely regular semigroup. For a finite set X, the top J -class J of P µ (X) is a right group. We find formulas for the ranks of the semigroups J, G ∪ I, J ∪ I, and I, where I is any proper ideal of P µ (X).