Indian police arrested four suspects in connection with serial blasts that killed two and injured 100 in Agartala, capital of the north-eastern state of Tripura, news reports said Thursday, dpa reported. Five blasts occurred Wednesday night within about 45 minutes in busy areas of the city, including markets and bus stops within a two-kilometre radius. Four arrests were made, the PTI news agency said, quoting an official statement. One of those detained was reportedly seen near one of blast sites. The statement did not give any further details on the suspects. All the blasts were of low intensity, local police said, adding that a sixth bomb had been found and defused. A number of secessionist rebel groups are active in north-eastern India. However, recent intelligence reports have suggested that units of the Bangladesh-based Islamic terrorist group Harkat-ul-Jehadi-ul-Islami have been infiltrating into north-eastern India. Major Indian cities have been hit by serial bomb blasts in 2008, including New Delhi, Jaipur and Gujarat.