Police in the southern Indian city of Bangalore say they have arrested a man in connection with last week's gun attack at a top science institute.
Police believe they have caught an accomplice of the gunman
Police believe the suspect helped the gunman who fired at delegates, killing a professor and wounding four others.
Prime Minister Manmohan Singh told India's annual Science Congress in the city of Hyderabad that the man killed was "a soldier of knowledge".
He said the attack was the work of "reprehensible and cowardly enemies".
Police say they detained the suspect, Abdul Rehman, on 1 January in his home town of Nalgonda in the neighbouring state of Andhra Pradesh, about 700km (435 miles) from Bangalore.
He appeared in court on Tuesday and was remanded in custody for 14 days.
Police say they are not yet sure what role the 35-year-old played in the attack, but expect the arrest to lead to "a major breakthrough".
"It is too early to say whether he was the mastermind or just an abettor," police commissioner Ajai Kumar Singh told the BBC.
He said police had information that he was a leader of the banned Lashkar-e-Toiba militant group in southern India.
Police say the suspect posed as a businessman and made frequent trips to Saudi Arabia. They have refused to release his picture, saying it could affect investigations.
The arrest is the first police have made since the gunman opened fire last Wednesday on delegates at a conference at the Indian Institute of Sciences (IIS) in Bangalore.
On Friday, they released a sketch of the gunman based on eyewitness accounts.
Opening the 93rd Indian Science Congress in Hyderabad, Prime Minister Singh condemned the attack in which Prof Puri died.
"Dr Puri was gunned down in the greatest temple of Indian science by the most reprehensible and cowardly enemies of our people," he told delegates.
He said "terrorists" were targeting India's research institutes because of the country's growing scientific and technical success.
More than 6,000 scientists from across India and abroad are attending the conference.
Security in the city is tight after two men suspected of planning attacks on police were arrested on Monday.