Adding to tensions, police in New Delhi said that on Thursday they arrested a man laden with explosives belonging to a group battling Indian rule in Kashmir. Indian and Pakistani troops also exchanged small arms fire across their disputed border.
Putin, visiting India to cement ties between the two long-term allies with nuclear power and arms deals, joined Manmohan Singh, the Indian prime minister, and thousands of spectators at a military procession in New Delhi that celebrates the founding of India's republic in 1950.
The New Delhi police spokesman, Deependra Pathak, said: "We are keeping an eye on threats. We all know ... the country ... and the kind of security environment we are living in."
In the past, separatists have marked the day by attacking security forces or the celebrations themselves.
The New Delhi parade, a showpiece of military might and cultural diversity, finished peacefully - the only "violence" being a carnivalesque re-enactment of Indians killing British officers during an 1857 rebellion against colonial rule.
Tight security arrangements were in place in Delhi, which was the scene of three bomb explosions in 2005 in which 66 people were killed - although these attacks did not occur on Republic Day. The attacks were blamed on separatists fighting Indian rule in Kashmir.
Police said they arrested a suspected member of Lashkar-e-Taiba, a group battling Indian rule in its part of Kashmir, who was carrying more than 2kg of explosives and two detonators outside a railway station.
On Thursday, a suspected member of a powerful separatists group in Assam, the United Liberation Front of Asom (ULFA), was killed when a bomb he was carrying exploded, while two other blasts left one dead and at least seven wounded.
The run-up to this year's Republic Day was marked by growing violence in Assam in which more than 80 people have been killed this month. Snipers were deployed on high-rise buildings in the state's main city, Guwahati, on Thursday.
|Russia's president, left, is visiting India to|
cement ties between the two nations [AFP]
Khagen Sharma, a senior police officer, said: "The militants are likely to launch timer-controlled bombs or grenade attacks."
Attacks claimed by the ULFA have killed more than 20,000 people since the group was formed in 1979. The northeastern region, with seven states, is home to more than two dozen separatist groups.
Security was also bolstered in Kashmir, where separatist fighting against Indian rule has killed more than 40,000 people since it began in 1989, according to officials. Human rights groups put the toll at around 60,000 dead or missing.
Security was also increased along the India-Nepal border, which police say has been used in the past for Pakistan- and Bangladesh-based fighters to cross into the country.
In the central state of Chhattisgarh, which is the epicentre of a Maoist insurgency in India, about 10,000 paramilitary personnel were deployed in the worst-hit Bastar region.