The horrific suicide attack on Pakistan's border post with India should be countered by "close cooperation" between the two countries, the CPI-M said Monday."This horrific attack underlines the threat posed by the extremist-terrorist groups in both Pakistan and India which needs to be countered by close cooperation between the two countries," it said in a statement.The Communist Party of India-Marxist conveyed condolences to families in Pakistan affected by the Sunday terror attack at Wagah at the time of the flag lowering ceremony.