The device exploded early Sunday, the Zimbabwean reported Monday.
The explosion came just days after President Robert Mugabe blasted Biti for refusing to provide funds for Zanu PF's populist policies.
"To him and some of his colleagues, agriculture is not an important area because they think that if they finance this sector they will be strengthening Zanu PF," Mugabe said. "They do not want to see the economy prospering."
Mugabe said Zimbabwe received $500 million from the International Monetary Fund and "we do not know what the money is being used for."
Biti reportedly said Zimbabwe is broke, with no foreign reserves, and its economy is struggling to recover following 10 years of crises. He said the IMF funds must be used to restore statutory reserves and to repair the nation's crumbling infrastructure, including roads, water, telephones and electrical production.