President Hamid Karzai said "enemies" of the strong friendship between Afghanistan and India had exploded a car bomb at the Indian embassy Monday that killed 40 people, including two senior diplomats.
India has been one of the strongest allies of post-Taliban Afghanistan, providing essential resources for reconstruction including for roads, electricity and other infrastructure.
"The president strongly condemned the terrorist attack against the Indian embassy in Kabul and considers it the work of enemies of Afghanistan-India friendship," a statement from his office said.
The statement did not specify who the "enemies of Afghanistan" were. Afghan officials often use this term to refer to Taliban and other extremists involved in a bloody insurgency against Karzai's Western-backed government.
Afghan and US officials often accuse circles in neighbouring Pakistan, India's long-time rival, of harbouring and supporting Taliban militants. Pakistan has strongly rejected the claim.
"Enemies of Afghanistan cannot stop expanding friendly relations by resorting to such attacks," the statement cited Karzai saying.
India's sprawling embassy compound in Kabul is a symbol of the country's bid for more strategic clout in Afghanistan since the fall of the extremist Taliban regime in 2001.
India's ramped-up presence in Afghanistan -- including the opening of consulates in several cities and resources for reconstruction -- has put it in competition with neighbour and long-time rival Pakistan, analysts say.
Pakistan condemned Monday's car bomb attack that targeted the Indian embassy in Kabul, but the Indian media and commentators have been quick to see it as a part of an intensifying Afghan feud between the rivals.
The nuclear-armed countries are officially at peace but are still seen by commentators as engaging in proxy tactics.
"Pakistan has a stated policy of seeking strategic depth in the region -- Afghanistan and beyond," said C. Uday Bhaskar, ex-deputy chief of the Institute of Defence Studies and Analysis in New Delhi.