An aide to Benazir Bhutto says the Pakistani opposition leader had planned to release proof of vote-rigging on the night of her assassination.

Latif Khosa, a senator from the opposition Pakistan People's Party,  said Tuesday Ms. Bhutto was to unveil the 160-page document at a press conference last Thursday night, after giving it to two visiting U.S. lawmakers. 

She was assassinated in a shooting and suicide bomb attack Thursday afternoon.

Khosa said he wrote the report titled "Yet Another Stain on The Face of Democracy" which presents evidence of vote-rigging ahead of the upcoming parliamentary elections. The document has not been released. 

He says the document shows Pakistan's main spy agency, the Inter-Services Intelligence, was working with the election commission and Pakistan's ruling party to fix the results of the polls.

Khosa also says U.S. financial assistance was being misused to rig the outcome.

Ms. Bhutto's party and her husband Asif Ali Zardari are demanding an independent, international inquiry into the opposition leader's death.

Some information for this report was provided by AFP, AP and Reuters.