German police say a Syrian man arrested after a two-day manhunt probably had links to so-called Islamic State (IS).
Jaber al-Bakr, who arrived in Germany as a refugee, was detained in a flat in the eastern city of Leipzig early on Monday. He had been tied up there.
He had sought help from another Syrian, who alerted police after letting Mr al-Bakr sleep at his flat, reports say.
The hunt began after police found very volatile explosives at Mr al-Bakr's flat in Chemnitz, south of Leipzig.
In the initial raid in Chemnitz early on Saturday, Mr al-Bakr, 22, evaded capture as officers fired a warning shot in a botched attempt to stop him.
"The methods and behaviour of the suspect suggest an IS context," said Saxony State Police chief Joerg Michaelis.
He said the suspect had researched bomb-making on the internet. "It is reasonable to assume that an explosives belt was nearly ready, or had been prepared already," he said.
Police found a detonator, explosives and a kilo of chemicals in the Chemnitz flat.
Mr Michaelis said the substance appeared to be TATP, a homemade explosive used in the deadly jihadist attacks in Paris last year and Brussels in March.
Security sources referred to Mr al-Bakr's apartment as a "a virtual bomb-making lab", and carried out a controlled explosion. German authorities feared a possible plan to target an airport in Berlin.
As the search for the suspect broadened, a police commando unit arrested another man in Chemnitz, blasting open the door of his home.
However, it was not until late on Sunday night that police were given a tip-off from another Syrian man living in Leipzig who had been contacted by Jaber al-Bakr from the city's main station.
At 00:42 on Monday morning, police burst into the flat in the Paunsdorf area of the city and found the suspect already tied up, Germany's Spiegel website reported.
Jaber Al-Bakr came to Germany in February 2015 and was granted asylum in November, German media say. He reportedly had links to the so-called Islamic State group. He is expected to be moved to the city of Karlsruhe later on Monday.
Over a million irregular migrants arrived in Germany last year, many fleeing the conflict in Syria. The BBC's Jenny Hill in Berlin says the latest incident will put pressure on Chancellor Angela Merkel to reassure a nervous German public that her decision to allow such large numbers into the country has not endangered the country.
A spokesperson for the German interior ministry said on Sunday: "We can't rule out in Germany such attacks that we've seen lately in France and Belgium."
The Bavarian CSU, allied to Mrs Merkel's ruling centre-right Christian Democrats, called on Monday for stricter security reviews for asylum seekers. The party called on the government to focus "even more intensively" in scrutinising migrants for potential extremists.