NEW DELHI, India (CNN) -- Police imposed a curfew in Jaipur on Wednesday, a day after near-simultaneous bomb attacks in the ancient Indian city killed at least 63 people and wounded more than 200.
Indian women mourn the death of their relatives in the May 13 serial blasts in Jaipur.
Vasundhara Raje, chief minister of Rajasthan -- the state of which Jaipur is the capital -- blamed an "unnamed international terror group" for the attack, but said it was too early in the investigation to specify which one.
H.G. Ragavendhra, Jaipur's superintendent of police, told CNN that police found nine newly-purchased bicycles at the scene, and think they were used to carry the explosives. The owner of the bike shop is helping police draw a sketch of the person who purchased them.
Police have also picked up six suspects and were questioning them.
Jaipur, known as the "pink city" for its rose-colored forts and palaces, is a popular tourist attraction. The majority Hindu city of 2.7 million people has a sizable Muslim population.
The day-long curfew, authorities said, was meant to prevent "communal violence."
It was intended to prevent large crowds from gathering at the blast site and hampering the investigation, said Jaipur police director Kanhaiya Lal. Also, tempers could flare as mourners spend the day carrying bodies to their home villages and to crematoriums, he said.
Home ministry officials suspect the Islamic militant group Harkat-ul-Jihad al-Islami (HuJi) of being behind the attacks, according to CNN's sister network CNN-IBN and the Press Trust of India. No one has claimed responsibility.
In the past, 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. See the aftermath of the explosions. »
Raje told reporters Wednesday that the military had been placed on alert and security tightened around the borders of the state, the western edge of which lies next to Pakistan.
She also took to task the central government, saying it had provided no advance warning about the possibility of such an attack.
Furthermore, Raje said, the central government left a state-proposed organized crime bill unapproved for two years. The bill would have allowed local police more leeway to interrogate suspects plotting attacks, she said.
On Tuesday evening, eight bombs tore through crowded markets and a packed Hindu temple in Jaipur's walled city. The blasts went off within a 12-minute span and within 500 meters (0.3 miles) of each other. Police defused a ninth bomb.
The Jaipur blasts bear an eerie resemblance in its pattern to a deadly attack two years ago in India's financial capital, Mumbai.
In July 2006, more than 200 people were killed when seven explosions targeted commuter trains in Mumbai, formerly Bombay. In that incident, the explosions went off within a span of 11 minutes.
Both attacks used RDX, one of the most powerful kinds of military explosives, and ammonium nitrate, an oxidizing agent in explosives.
And both attacks took place during the evening hours and on Tuesdays.
The Jaipur blasts occurred near the temple on a day when devotees pray to Hanuman, the Hindu monkey king. Nearby markets and bazaars that were also targeted were filled with tourists and locals.
In the Mumbai attack, the blasts were timed to go off during the height of rush hour. And authorities said the bombs all appeared to have been planted on trains that left the Churchgate station -- used daily by thousands of commuters in the metropolis of more than 11 million people.
Indian officials blamed Pakistan's intelligence services and a Pakistan-based militant group, Lashkar-e-Tayyiba, for the attack. Pakistan, which banned Lashkar-e-Tayyiba in 2002, denied any involvement.
The Jaipur blast has one more element in common with yet another deadly attack: the use of bicycles.
Just as on Tuesday, assailants used bombs strapped to bicycles in an attack at a mosque in the western Indian city of Malegaon in September 2006.
At least 33 people were killed and more than 100 wounded in that explosion, which took place on a Friday -- when the mosque is filled with Muslim worshippers. That attack was also blamed Lashkar-e-Tayyiba.
Authorities have not connected the Jaipur blast to any previous attacks.
HuJi -- or the Movement of Islamic Holy War -- is considered a terrorist organization by the United States.
It is banned in neighboring Bangladesh, where it is accused of carrying out several attacks, including a foiled plot to kill the country's former Prime Minister Sheikh Hasina in 2000.
And it has been blamed for several attacks inside India, including one at the American Center in Calcutta that killed five policemen in 2002.
India ranks among the countries where terrorism is most common, the U.S. State Department said.
"The conflict in Jammu and Kashmir, attacks by extreme leftist Naxalites and Maoists in eastern and central India, assaults by ethno-linguistic nationalists in the northeastern states, and terrorist strikes nationwide by Islamic extremists took more than 2,300 lives this year," the agency said.
CNN's Tess Eastment and Saeed Ahmed contributed to this report.