US Secretary of State Condoleezza Rice has told Pakistan that there is "irrefutable evidence" of involvement of elements in this country in the Mumbai terror attacks and it had no option but to act urgently and effectively to avert a strong international response.

Rice "pushed" the Pakistani leaders to move against the perpetrators of the terror strikes warning that "otherwise, the US will act", the Dawn reported on Saturday. 

The clear message was conveyed to Pakistan's top leadership by Rice during her brief stopover in Islamabad on Thursday, diplomatic sources said, giving credence to the report.

Rice said that there was "irrefutable evidence" of the involvement of Pakistani elements in the Mumbai attacks, the sources said.

She travelled to Pakistan after a visit to India, where she was shown the extensive evidence gathered by investigators to prove the linkages between the Mumbai attackers and Pakistan-based elements, especially the banned Lashker-e-Taiba terror group, the sources said.

 They said Rice, during her interactions with President Asif Ali Zardari, Prime Minister Yousuf Raza Gilani, Foreign Minister Shah Mehmood Qureshi and army chief Gen Ashfaq Parvez Kayani, made it clear that Pakistan needs to act effectively to bring the perpetrators to justice.