NEW DELHI, Jan. 26 (Xinhua) -- Four blasts took place Sunday morning in India's northeastern state of Assam as the country began to celebrate its Republic Day, with no casualties reported so far, according to the police.

The police said three blasts went off at three places in Dibrugarh district, about 424 km northeast of Dispur, the capital city of Assam, and the other one took place in adjacent Charaideo district.

"The blast took place between 8:15 a.m. (local time) and 8:25 a.m (local time)," a police officer said. "Since it was a holiday in view of Sunday and Republic Day, people were mostly indoors, which I think was the reason the blasts didn't cause any casualty."

Following the blasts, which were suspected to be caused by grenades, police teams rushed to the spots and collect forensic evidence to unravel the nature of blasts.

"There have been four low-intensity IED blasts in Upper Assam. There has been no casualties or damage to property. We would leave no stone unturned to neutralise the perpetrators. That's our solemn assurance to people," a senior police official GP Singh said.

Assam Chief Minister Sarbananda Sonowal condemned the blasts and vowed to take strong action against the culprits.

"Strongly condemn the bomb blasts in a few places of Assam. This cowardly attempt to create terror on a sacred day only exhibits the frustration of the terror groups after their total rejection by the people," said Sonowal in a brief statement posted on twitter, adding that the government will take the "sternest action."

With an armed insurgency going on in India's northeastern states, dozens of insurgent groups have challenged New Delhi's rule in the region and waged a guerrilla war. While some armed groups fighting Indian troops demand a separate homeland, the others seek regional autonomy.

The blasts took place ahead of the India's Republic Day function in the state.

Every Jan. 26 is celebrated as the Republic Day in India as it marks adoption of the constitution in the country. The main celebration was held in New Delhi, where India's army, navy and air force display their skills and military might.

Authorities have beefed up security and made adequate arrangements across the country to ensure Republic Day functions pass off peacefully.