Chancellor Angela Merkel has said Germany needs more video surveillance and a national database of terror suspects after a bomb plot was foiled.
The detained Lebanese student is believed to have accomplices
A 21-year-old Lebanese student was arrested on Saturday in the northern city of Kiel, on suspicion of planting bombs on two trains last month.
German prosecutors said on Monday the tip-off leading to his arrest had come from Lebanese military intelligence.
Police are still searching for an unidentified accomplice.
"I think we must quickly develop the anti-terror database," Chancellor Merkel said.
She said the identification of the Lebanese suspect through closed-circuit TV footage also showed how important video surveillance cameras were.
Interior Minister Wolfgang Schaeuble is planning to further strengthen German counter-terrorism laws.
The devices in abandoned suitcases on two trains failed to go off. Police said the bombers had intended to kill many people.
German police released security camera footage on Friday
In the video, the two suspects are seen wheeling suitcases at Cologne station.
DNA traces on one of the suitcases also helped identify the Lebanese student as a suspect, prosecutors said. He was identified only as Youssef Mohammed E H.
Investigators first thought the bombs were part of a blackmail attempt, but they now believe the incident was the work of a terrorist group based in Germany.
A note written in Arabic, a telephone number in Lebanon, and packets of starch with labels in Arabic and English were found alongside the devices.
The authorities say they are investigating a possible link to Lebanon.
The identical suitcase bombs were fitted with timers set to go off 10 minutes before the trains arrived in Dortmund and Koblenz.
Police think they failed to detonate because of a construction flaw.
Security has since been stepped up at German airports, and the rail authorities have announced they are installing more closed circuit TV cameras at stations.