(KUNA) -- At least seven persons have been killed in a powerful bomb explosion triggered by suspected insurgents in Imphal East district in India's Northeastern state of Manipur. A powerful bomb exploded at Pourabi in Imphal East district late Sunday night when a bus was passing through the area in which seven persons were killed, news agency Press Trust of India reported Monday. Following the blast, security has been tightened across Manipur, which borders Myanmar. No rebel group has so far claimed responsibility for the attack. This is the second such blast in the past one month in Manipur. On November 16, insurgents exploded a powerful bomb at a shop in the crowded Paona market complex in Manipur's Imphal town, killing one civilian and injuring four others. Meanwhile, Indian Home Minister Shivraj Patil in a statement at Delhi today said: "I strongly condemn the bomb blast which took place in Manipur. I convey my sympathies to the kins of those killed. Such desperate acts by anti-national elements will not help them in any manner and will only isolate them further. I am confident that the Manipur Government will take all steps to avoid recurrence of such incidents and bring the culprits to book." Manipur is home to more than 20 insurgent groups whose demand ranges from secessionism to greater autonomy.