John Chiligati, Deputy Minister for Home Affairs, said weekend attacks on the homes of political and religious leaders and a restaurant used by tourists were political, not religiously motivated as the police previously suggested.
"We have found out that these attacks are not religious. They have all the signs of being political," he said during a tour of the island. "From now on I am outlawing any military training undertaken by any political party."
Tanzania's main opposition political party, the Civic United Front (CUF), which draws most of its support from among the island's Muslim communities, maintains a quasi-military youth wing known as the Blue Guards.
Chiligati said places of worship would also be searched regularly to stop them being used for military training.
The ruling party on Zanzibar and the Tanzanian mainland, the Chama cha Mapinduzi (CCM-Party of the Revolution), has blamed the Guards for bomb attacks during elections in 1995 and 2000.
"The message is very clear. They want to destroy the government's image and economy"
deputy minister for home affairs, Tanzania
Dozens of people were killed in political clashes in 2001, and tensions between the two political rivals are mounting ahead of general elections to be held next year. But a CUF spokesman denied his party was giving its followers any military training.
"We do not have that ability," Salim Biimani said. "It is the contrary: It is the ruling Chama cha Mapinduzi which has been making military preparations." The CCM denies that charge.
Thirty-nine people were arrested after homemade bombs detonated over the weekend at houses belonging to a Zanzibari cabinet minister and the island's top Islamic leader, but no one has been charged.
A grenade thrown into Mercury's, a busy seafront restaurant, landed on the table of a British diplomat but failed to explode. The attacks followed bombings last week of a church, a school bus and a number of electric transformers.
"The message is very clear," Chiligati said. "They want to destroy the government's image and economy."
CUF says it has written to the government in the past seeking its view on where the constitution stands on militia-style training by political parties but got no response.