A parliamentary candidate of a liberal party was shot dead by gunmen Friday in the Pakistani port city of Karachi in a latest pre-election targeted attack, his party and police said. Sadiq Zaman Khattak, candidate for a National Assembly seat of the ethnic Pashtoon \"Awami National Party\' (ANP) came under attack as he walked out of mosque after Friday prayers in Korangi area, spokesman of the party, senator Zahid Khan said. Khattak\'s six-year old son Aiman Khattak was also killed, and another son was injured in the attack. The gunmen, riding a motorcycle, fled after the attack, witnesses said. Police said that five people, including two guards of the slain ANP candidate, were injured. Witnesses said the gunmen had been waiting outside the mosque and opened fire on him as he emerged from the mosque. Pakistani Taliban claimed responsibility for the attack. Taliban spokesman, Ehsanullah Ehsan, said the attack is part of the militants\' plan to target what he called secular parties. The Taliban had threatened attacks on the ANP, Pakistan Peoples Party of President Asif Zardari and the ethnic Urdu-speaking \" Mutahida Qaumi Movement\" for their support for security forces\' operations against the militants. It is the third candidate that has been be killed during election campaign. Two provincial assembly candidates were killed in Sindh and Balochistan provinces.