A major tragedy was averted in this southern city as five bombs were defused by police who, sources said, had also arrested four suspects and seized a haul of explosives during the last two days.

Police said the Jaish plot came to light in a breakthrough after the interrogation of three youths arrested in connection with a suicide bombing attack in the city on October 12.

Prime Minister Manmohan Singh arrives in Hyderabad on Monday night for a one-day visit amid tight security.

On Tuesday morning, the Prime Minister flies in a chopper to inaugurate the 93rd Indian Science Congress at the Acharya NG Ranga Agriculture University (ANGRAU) at Rajendranagar on the outskirts of the city and presents the outstanding scientists award.

Police on Sunday arrested Syed Haji and Shujauddin from the Mosarambagh neighbourhood and seized a 10-kg tiffin bomb and other materials used to trigger a blast. Three bombs, seized from one Shakeel Ahmed in the Laad Bazar area near the historic Charminar, were also defused, police sources said.

The fifth bomb that Shakeel had delivered in Zaheerabad in Medak district was also recovered and defused after arresting a man, while yet another bomb sent to Bidar in neighbouring Karnataka was yet to be traced.

While the police are yet to officially announce the arrests and seizures, the sources said they found material used to make bombs.

The mastermind behind the plot is said to be one Shahed, brother of one of the accused arrested earlier in the suicide bombing case and identified as Zahid.

Police have not ruled out a link between this terror module and the last week's terror attack on Indian Institute of Science (IISc) in Bangalore, in which one professor was killed and three others were injured.