Condemning the attack by terrorists on a hotel in Islamabad [Images], Prime Minister Manmohan Singh [Images] on Sunday said such forces threaten democracy, peace and development in both countries and should not be allowed to succeed.

"Such attacks are a grim reminder of the challenges we face from destructive forces, which have pitted themselves against the values of democracy and pluralism and the voices of moderation," Dr Singh said in a letter to his Pakistani counterpart Yousuf Raza Gilani [Images].

Expressing his deep shock and sorrow at Saturday's attack on the Marriott Hotel, he said, "We strongly condemn this act of terrorism. They threaten the peace, stability and development of each of us individually and all of us collectively.

We must not allow such forces to succeed. They must be dealt with and brought to justice," Dr Singh added.