NEW DELHI, India (CNN) -- A little-known group called Indian Mujahideen has claimed responsibility for Tuesday's near-simultaneous bomb attacks that killed 63 people in the northwest Indian city of Jaipur. It also warned of more attacks in the country.
Indian women mourn the death of their relatives in the May 13 serial blasts in Jaipur.
The group sent an e-mail and video clips, claiming responsibility, to a Hindi cable news channel, Jaipur police Inspector General Pankaj Kumar Singh told CNN Thursday.
Authorities are checking the authenticity and credibility of the claims, he said.
"Once we investigate that," Singh said, "we move ahead and try to find the source -- whether it's an old group with a new name, an off-shoot of another group, or a new one completely."
Eight bombs went off within 12 minutes and within 500 meters (0.3 mile) of each other Tuesday. They tore through crowded markets and a packed Hindu temple, killing at least 63 people and wounding more than 200. Police defused a ninth bomb. See the aftermath of the explosions »
Jaipur remained under a curfew Thursday to prevent "communal violence," officials said. The majority Hindu city of 2.7 million people has a sizable Muslim population.
In the e-mail, Indian Mujahideen declared an "open war" against India -- retaliation, it said, for 60 years of Muslim persecution and for the country's support of U.S. policies.
"This letter is an open warning to you that if you continue to arrest the innocent Muslims then those days are not far away when we will slaughter you on the streets of DELHI, MUMBAI, KOLKATA, CHENNAI and other states of India," it said.
The group said it targeted Jaipur "to blow your tourism structure and to demolish your faith in" Hindu gods.
Jaipur, knows as the "pink city" for its rose-colored forts and palaces, is a popular tourist destination.
The blasts went off near a Hindu temple where devotees pray to Hanuman, the Hindu monkey king, every Tuesday. They also targeted markets frequented by foreigners.
"From a tourism point of view this attack is to warn the entire crusaders of the world, U.S. and BRITAIN in particular, we [M]uslims are one across the globe and don't send your people to India and if you do so then you people will be welcomed by our suicide attackers," the e-mail said.
One of the short video clips accompanying the message showed a bicycle parked in a market with a bag in its rear carrier. The group said the bicycle was used in the attacks.
Police found nine newly-purchased bicycles at the scene that they think were used to carry the explosives. The owner of the bike shop helped police draw a sketch of the person who purchased the bicycles. Police continue to look for him.
Security analysts say Indian Mujahideen is a relatively-unknown group. It may be a new home-grown terror network, an alias for an existing group or for a foreign militant organization.
On Wednesday, CNN's sister network, CNN-IBN, and the Press Trust of India news agency said home ministry officials suspect the Islamic militant group Harkat-ul-Jihad al-Islami (HuJi) -- or the Movement of Islamic Holy War -- of being behind the attacks.
Cross-pollination among various terror groups makes it difficult to separate them, analysts say.
"There is a thin line that differentiates these groups," said Sumon K. Chakraborti, national affairs correspondent for CNN-IBN. "They often operate on the same resources."
Among the few times Indian Mujahideen surfaced to take responsibility was last November, when near-simultaneous blasts went off outside courts in three north Indian cities in the state of Uttar Pradesh.
The explosions killed more than a dozen people and injured 80.
As in the Jaipur attacks, assailants last November used a bicycle to carry explosives in one of the attacks.
India ranks among the countries where terrorism is most common, according to the U.S. State Department.
In the past, Indian officials have blamed attacks within its borders on "foreign" Islamic extremist groups fighting against Indian rule in the disputed Himalayan territory of Kashmir. It is a term that is commonly understood to refer to Pakistan.
Kashmir has been the source of bitter dispute and two wars between India and Pakistan. Both control parts of the region, which is predominantly Muslim.
Pakistan has denied any involvement in the attacks.
Tess Eastment in New Delhi and Saeed Ahmed in Atlanta contributed to this report