Inverse problems of identifying the unknown spacewise and time dependent heat sources Fix) and H(t) of the variable coefficient heat conduction equation u(t) = (k(x)u(x))(x)+ F(x)H(t) from supplementary temperature measurement (u(T)(x):=u(x,T-f)) at a given single instant of time T-f > 0, are investigated. For both inverse source problems, defined to be as ISPF and ISPH respectively, explicit formulas for the Frechet gradients of corresponding cost functionals are derived. Fourier analysis of these problems shows that although ISPF has a unique solution, ISPH may not have a unique solution. The conjugate gradient method (CGM) with the explicit gradient formula for the cost functional J(1)(F) is then applied for numerical solution of ISPF. New collocation algorithm, based on the piecewise linear approximation of the unknown source H(t), is proposed for the numerical solution of the integral equation corresponding to ISPH. The proposed two numerical algorithms are examined through numerical examples for reconstruction of continuous and discontinuous heat sources F(x) and H(t). Computational results, with noise free and noisy data, show efficiency and high accuracy of the proposed algorithms. (C) 2011 Elsevier Ltd. All rights reserved.