Angela Merkel is to come under renewed criticism of her open-door immigration policy after another horrific attack on German soil.

Last night a Syrian refugee wielding a machete killed a pregnant woman and injured two other people before being arrested by police.

The attack happened in the south western city of Reutlingen near a doner kebab stand in a bus station at Listplatz Square.

Angela Merkel is to come under renewed criticism of her open-door immigration policy after another horrific attack on German soil

Police arrest a man who is believed to have gone on a machete rampage killing a woman in the German city of Reutlingen

German media have been reporting that the motive for the attack in the city south of Stuttgart was unclear.

The attack comes just days after a young Afghan swung an axe at passengers on a train in Bavaria.

The 17-year-old, who a witness said shouted 'Allahu Akbar' (God is Great) during the attack, severely wounded four Hong Kong residents on the train late on Monday, then injured a local woman after fleeing, before police shot him dead.

He had entered Germany last summer with waves of migrants, raising more questions about Chancellor Merkel's open-door refugee policy. Around one million migrants came to the country in 2015, many fleeing war in Afghanistan, Syria and Iraq.

Elsewhere a 27-year-old bomber, a Syrian man, blew himself up close to a German music festival in an 'Islamist suicide attack' - the third bloody attack on the country in the past week.

Attack: A 27-year-old suicide bomber, a Syrian man who was denied asylum in the country, injured 12 people in a packed wine bar attack in Ansbach, near Nuremberg last night

A special police officer examines a backpack at the entrance of a building in Ansbach, Germany, believed to have contained the deadly bomb

An ambulance takes away one of the 12 injured in the Ansbach wine bar - three are in a serious condition in hospital

The man killed by an explosion at a bar in the southern German city of Ansbach was the one who set off the blast, local police said

Investigators this morning descended on a flat in the town where the 27-year-old attacker is understood to have lived

The Syrian man who was denied asylum in the country, injured 12 people outside a packed wine bar in Ansbach, near Nuremberg at 10pm last night.

The unnamed bomber was turned away from an open-air music festival filled with 2,500 people because he did not have a ticket.

Instead he walked to a bar in the centre of Ansback and detonated a DIY bomb filled with metal shavings and screws. He died and 12 others were injured, three seriously.

The attack came just days after a young Afghan swung an axe at passengers on a train in Bavaria.

The viscous cases are likely to further deepen worries about so-called 'lone wolf' attacks in Europe and could put political pressure on Merkel.

The Afghan attacker came to Germany as an unaccompanied minor and was registered as a refugee on June 30 last year in Passau.

Frank Decker, political scientist at Bonn University, said: 'In the minds of many people, his arrival is directly linked to Merkel and her liberal refugee policies.'

The attack took place days after a Tunisian delivery man ploughed a lorry into crowds of Bastille Day revelers in Nice, killing 84. ISIS has claimed responsibility for the mass murder.

Emergency services at the scene of the machete attack in Reutlingen where a pregnant woman was killed

The 17-year-old axe attacker who registered in Germany as Riaz Khan Ahmadzai (pictured) and may have lied about being an Afghan refugee in order to claim asylum in the country

Public support for Merkel has risen since Britain voted on June 23 to leave the European Union, helping reverse a fall in her popularity caused by the refugee crisis. Mr Decker said a Nice-style attack here could quickly end those gains.

'It would boost those who have called Merkel's policies a mistake,' he said. 'Merkel would be blamed.'

Unlike France and Belgium, Germany has not been the victim of a major attack by Islamic militants in recent years, although security officials say they have thwarted a large number of plots.

A leader of the far-right, anti-immigrant, Alternative for Germany (AfD) said Merkel and her supporters were to blame for the dangerous security situation because their 'welcoming policies had brought too many young, uneducated and radical Muslim men to Germany'.

Imam Arbab Ahmad, whose mosque in Wuerzburg lies about seven miles from the scene of the train attack, said he feared a backlash against Muslims.

'I am anxious,' he said. 'It was a totally inhumane attack on innocent people. Every human being should condemn it, not just Muslims.'

Before tonight's attack senior German officials called for a review of gun laws and even stricter enforcement after Friday's shooting in Munich.

German Vice Chancellor Sigmar Gabriel said: 'Gun control is an important issue. We must continue to do all we can to limit and strictly control access to deadly weapons.'

The German Interior Minister Thomas de Maiziere vowed to review German gun laws after studying an investigation into the attack, and to seek improvements where needed.