The Italian ambassador Mariani had a head injury and was admitted to the Batticaloa hospital while the US envoy had minor injuries, doctors said.
Sri Lankan cricketer Dasun Shanaka revisited the Easter Sunday horror, the serial blasts that took place in the country on Sunday, leaving almost 300 people dead and more than 500 injured.
Seven persons had been arrested in connection with the blasts.
"My heart goes out to the families of the victims and the injured," Modi said.
The two countries also signed memoranda of understanding in education and health sectors after visiting External Affairs Minister Sushma Swaraj and her Lankan counterpart Mangala Samaraweera co-chaired the 9th Indo-Lanka Joint Commission meeting in Colombo.