In a message on Sunday, Salehi expressed condolences to the Pakistani government, nation and the bereaved families of the pilgrims killed in the terrorist attack.
On Sunday, at least 19 people were killed when a bomb ripped through a convoy of three buses carrying Shia pilgrims in the Mastung district, some 30 kilometers (18 miles) south of Quetta in Balochistan Province.
According to reports, a number of women and children were among the victims. A senior government official in Quetta said the buses were carrying some 180 Shia pilgrims, who were on their way to Iran.
Attacks against Shia Muslims in different parts of Pakistan have escalated in recent months. Since the beginning of 2012, hundreds of Shias have been killed in the country.
Last month, many Shia Muslims were killed in several attacks targeting processions held to commemorate the martyrdom of the third Shia Imam, Imam Hussein (PBUH).
Pakistani Shia leaders have called on Islamabad to form a judicial commission to investigate the bloodshed.
According to Human Rights Watch, the Pakistani government has failed to stop the violence against Shias, who account for around 20 percent of the country’s 167-million-strong population.