German Chancellor Angela Merkel interrupted her holiday to defend her open-door refugee policy, defiantly reinforcing her "we can do this" mantra, after her approach came under criticism following several deadly attacks involving asylum seekers.

Merkel held a news conference in the middle of her summer break to set out her intention to continue with the migrant policy that has seen over a million refugees seek asylum in Germany in the past year.

She repeated the mantra of "Wir schaffen das", or "we can do this," a phrase she adopted last summer when Germany opened its doors to migrants fleeing wars in the Middle East.

"We can do this and we have already done a lot over the past 11 months," she said.

"The terrorists want to make us lose sight of what is important to us, break down our cohesion and ... our willingness take in people who are in need," Merkel said.

"They sow hatred and fear between cultures and they sow hatred and fear between religions. We stand decisively against that," she continued.

There have been five deadly attacks committed in Germany since July 18 that have left 15 people dead - including four attackers - and dozens injured.

The attacks in Germany have led to accusations from Merkel's critics - and even some allies - that her open-door refugee policy is to blame for these deadly attacks. But the Chancellor said she felt she had "acted responsibly and correctly".

Two recent attacks have been been carried out by asylum seekers with links to Islamist militancy. A Syrian who had been denied asylum blew himself up in Ansbach, injuring 15, while a teenage refugee from Afghanistan left five people wounded after attacking them with an axe on a train in Bavaria.Merkel condemned the two attackers for mocking Germany and the other asylum seekers the country has welcomed.

The Chancellor batted away questions about why she hadn't visited the scene of any of the five deadly attacks, telling the packed news conference that she would be attending a memorial ceremony on Sunday in Munich, the scene of the bloodiest of the attacks in which an 18-year-old German-Iranian gunman killed nine people in a shopping centre. Officials have confirmed that the lone gunman, Ali David Sonboly, had no links to the so-called Islamic State.

"Angst cannot be the guide for political action," Merkel said, setting out a nine-point plan to respond to the attacks, including measures to recruit more staff for security agencies and an early warning system for the radicalisation of refugees.

Reassuring Germans that their safety was paramount, she added: "We will take the necessary measures and ensure security for our citizens. We will take the challenge of integration very seriously."