German chancellor Angela Merkel has offered Turkey financial aid and the prospect of faster progress on its bid to join the European Union in return for badly-needed help in stemming the flow of asylum seekers to Europe.

Speaking in Istanbul at a joint news conference with Turkish prime minister Ahmet Davutoglu, Ms Merkel said Germany could help accelerate the path to visa-free travel to the EU for Turks and push forward Ankara's protracted EU membership talks.

Key points: Merkel visits Turkey to further EU accession talks

Merkel visits Turkey to further EU accession talks Turkey taking EU-rejected asylum seekers among the conditions

Turkey taking EU-rejected asylum seekers among the conditions Turkey's PM says there are differences to be resolved first

Turkey's PM says there are differences to be resolved first Stabbed politician becomes mayor of Cologne

In return, she expected Turkey to agree to take back asylum seekers rejected by the EU, something Mr Davutoglu has said he would only agree to if there was progress on the visa issue.

"I think we have used the crisis we are experiencing through a very disorderly and uncontrolled movement of refugees, to again achieve closer cooperation on many issues, both between the European Union and Turkey, and between Germany and Turkey," Ms Merkel said after meeting the Turkish prime minister.

Dubbed a "punch-bag" for her own party by some German media due to frustrations over the asylum seekers crisis, Ms Merkel wants to cement a European deal with Turkey on aid and closer ties in return for help in encouraging asylum seekers there to stay put.

She has resisted pressure to tighten Germany's border controls and turn away asylum seekers arriving from Austria, even as Germany expects 800,000 to 1 million new arrivals this year.

Both the Turkish and German leaders said they had agreed there could be no lasting solution to the asylum seeker crisis without resolving the conflict in Syria, from where more than 2 million asylum seekers have now fled to Turkey.

Sorry, this video has expired Turkey expert Sinan Ulgen discusses the conditions and significance of an EU-Turkey deal.

A "safe zone" in northern Syria, a proposal long championed by Turkey but which has gained little international traction, is badly needed if the flow of asylum seekers is to be stemmed, Mr Davutoglu said, warning of a potential new wave of migration as fighting intensifies around the Syrian city of Aleppo.

"Our priority is to prevent illegal immigration and reduce the number of people crossing our borders," Mr Davutoglu said.

"In that respect we have had very fruitful discussions with the EU recently."

But he said that while progress had been made on an EU offer to Turkey last week of an action plan including "re-energised" talks on joining the bloc, as well as aid and the prospect of easier travel visas, several issues remained unresolved.

Visa-free travel for Turks should be brought forward to July 2016 instead of the current planned 2017 in return for Turkey signing a "readmission agreement" to allow in asylum seekers sent back from Europe, he said.

Turkey should also be allowed to participate in EU summits, he added.

"Germany is ready to offer support. If we take the question of visa liberalisation, we can talk in the German-Turkish working group... about specific possibilities to push through visa facilitation," Ms Merkel said.

Just two months ago, Ms Merkel was practically able to dictate terms to Greece over an aid plan to tackle its debt crisis.

But with neighbouring Turkey, she has far less leverage to get her way, particularly as just 10 days ago, she reiterated her opposition to Turkey joining the European Union.

Pro-refugee politician stabbed, wins election

In Germany, a pro-refugee politician who was stabbed in the neck while on the campaign trail has been elected the first female mayor of Cologne.

Henriette Reker, an independent supported by Ms Merkel's ruling Christian Democrats party, is expected to make a full recovery after being seriously injured in what police labelled a "racist, political attack".

The attack against Henriette Reker came as Germany struggles to cope with a record influx of asylum seekers. ( AFP: DPA: Oliver Berg )

Her attacker, a 44-year-old unemployed man known to be close to the extreme right in the 1990s, was arrested at the scene of the crime.

According to Der Spiegel magazine, the suspect told police that "foreigners are taking our jobs" and warned that Islamic Sharia law would soon hold sway in Germany.

The attack on Saturday sparked a national outcry and turned the 58-year-old trained lawyer into Germany's most prominent victim of a growing backlash against the asylum seeker influx.

For the past five years, Ms Reker has been responsible for running refugee services in Cologne, Germany's fourth-largest city with 980,000 inhabitants including a sizeable Muslim minority.

In charge of accommodating asylum seekers from Syria and other war zones, she has housed them in sports halls, former commercial spaces and other sites, and has called for their social integration.

Reuters/AFP