German police arrest two over plot to attack shopping centre

Police have arrested two brothers on suspicion of planning to attack one of Germany's biggest shopping centres, authorities said Friday, four days after a 12 people were killed at a Berlin Christmas market.

Police said they had arrested two men, aged 28 and 31, originally from Kosovo, and were trying to establish how advanced the plot was and whether other people were involved.

The brothers were arrested in the city of Duisburg after information provided by security sources, police said in a statement.

Acting on a tip-off from the intelligence services, police were deployed to the shopping complex and a nearby Christmas market in the western city of Oberhausen late Thursday, they said.

The shopping centre that was targeted, CentrO, is one of the largest in Germany with around 250 shops that are usually packed in the run-up to Christmas.

The arrests come as police frantically hunt for the Tunisian suspect accused of ploughing a truck through crowds packing one of Berlin's most popular Christmas markets on Monday.

The Islamic State group has claimed the attack, which would be their deadliest yet carried out on German soil.

Police commandos on Thursday raided three homes and a long-distance bus, prosecutors said, as they cast a wide dragnet for 24-year-old Anis Amri.

Police say they are certain it was Amri who steered the 40-tonne lorry after finding his identity papers and fingerprints inside the cab, next to the corpse of its registered Polish driver who was killed with a gunshot to the head.

Authorities have issued a Europe-wide wanted notice over the attack, offering a $100,000 reward for information leading to Amri's arrest.

Investigators believe Amri was still lying low in Berlin because he is probably wounded and would not want to attract attention, Der Tagesspiegel reported citing security sources as saying on Friday.

In Tunisia, a brother of the fugitive appealed to him to surrender.

"If he is listening to me, I tell him: 'Present yourself' so the family can rest easier," Abdelkader Amri said.

"If my brother is behind the attack, I say to him 'You dishonour us'," he said.

Chancellor Angela Merkel said she was "proud of how calmly most people reacted" to Germany's deadliest attack in years and voiced confidence Amri would be arrested soon.

But her message failed to dampen criticism of what many politicians and newspapers slammed as glaring security failures leading up to Monday's attack.

Officials have revealed that Amri was a rejected asylum seeker with a history of crime who had spent years in an Italian jail and had long been known to German counter-terrorism agencies.

News weekly Der Spiegel reported that in wiretaps, Amri could be heard offering to carry out a suicide operation, but that his words were too vague for an arrest warrant.

And Berlin prosecutors said Amri had been monitored from March until September, suspected of planning a burglary to pay for automatic weapons to carry out an attack.

However, when authorities failed to find evidence of the plot and watched Amri operate as a small-time drug dealer, the surveillance was stopped.

"They knew him. They did nothing," ran a headline of Berlin's BZ newspaper.

Conservative politician Stephan Mayer, a critic of Merkel's liberal stance on refugees, said the case "held up a magnifying glass" to the failings of her migration policy.

Germany took in more than a million refugees last year, many of them fleeing violence in Syria, North Africa and the Middle East.

"It's clear that a lot went wrong... it was a systemic failure," said Peter Neumann, professor of security studies at King's College London.

Neumann argued that German security services lacked the manpower to maintain around-the-clock surveillance of the 550 known radical Islamists in Germany.

"Germany's anti-terrorism structure is failing to match the scale of the problem," he told news channel NTV.