GUWAHATI (AFP) - A spate of blasts rocked northeast Indias Assam state Monday, killing eight people and wounding 60 on the eve of a visit to the restive region by Prime Minister Manmohan Singh, police said. A bomb exploded in a crowded market in Assams largest city, Guwahati, around 1:45 pm (0815 GMT), killing seven people and wounding 30 more, a police spokesman said. The bomb was planted on a parked motorcycle, spokesman G.P. Singh said. Witnesses said the area was packed with people when the explosion occurred and that several school children on their way home were among the injured. The official said there were three other bomb explosions and two grenade attacks elsewhere in Assam state, including one at a police station. A police officer injured in one of the two grenade attacks died of his injuries while 30 others were hurt in the blasts, the spokesman said. Police blamed the outlawed United Liberation Front of Assam (ULFA) for the explosions. The blast comes a day before the ULFA marks its 30th foundation day and we had intelligence inputs about the group planning some attacks in the city, officer Singh said. The prime minister was scheduled to visit Assam on Tuesday to address an election rally. This is a barbaric act and we have asked the police to take firm action, Assam Chief Minister Tarun Gogoi said as New Delhi asked his administration to tighten security ahead of national polls set to begin April 16.