Berlin - German Chancellor Angela Merkel on Thursday "firmly" rejected calls to reverse her welcoming stance toward refugees following a series of brutal attacks in the country.Merkel told reporters that the assailants "wanted to undermine our sense of community, our openness and our willingness to help people in need". "We firmly reject this," she said.Merkel, who interrupted a summer holiday at her cottage north of Berlin to face the media in the capital, told reporters that four brutal assaults within a week were "shocking, oppressive and depressing" but not a sign that authorities had lost control."Taboos of civilisation are being broken," she said, referring to a series of deadly attacks in France, Belgium, Turkey and the US state of Florida as well as Germany."These acts happened in places where any of us could have been."But she repeated her rallying cry from last year when she opened the borders to people fleeing war and persecution, many from Syria, which brought nearly 1.1 million migrants and refugees to the country in 2015."I am still convinced today that 'we can do it' - it is our historic duty and this is a historic challenge in times of globalisation," she said. "We have already achieved very, very much in the last 11 months."Merkel was speaking after a axe rampage, a shooting spree, a knife attack and a suicide bombing stunned the country, leaving 13 dead, including three assailants, and dozens wounded.Three of the four attackers were asylum seekers, and two of the assaults were claimed by the Islamic State group (ISIS).'Urgent action' While the German political class has largely called for calm, opposition parties and rebels from Merkel's own conservative bloc have accused her of exposing the country to an unacceptable level of risk without stricter controls on new arrivals."Islamist terrorism has unfortunately arrived in Bavaria," the state's interior minister Joachim Herrmann told reporters Thursday, renewing calls by his Christian Social Union party for an upper limit on new asylum seekers let into Germany."We are awaiting urgent action from the federal government and Europe - now is the time to act."The deadliest attack came on Friday when a German-Iranian teenager who was born and raised in Munich opened fire at a downtown shopping mall, killing nine people before turning the gun on himself.He had been under psychiatric treatment and investigators say he was obsessed with mass shooting, including Norwegian rightwing fanatic Anders Behring Breivik's 2011 massacre. They have ruled out an Islamist motive, saying the assailant had far-right "sympathies".On July 18, an asylum seeker from Afghanistan or Pakistan slashed train passengers and later a passer-by with an axe and a knife in Wuerzburg before being shot by police.And on Sunday, a Syrian failed asylum seeker blew himself up outside a music festival, wounding 15 people at a nearby cafe after being turned away from the packed open-air venue. IS claimed both attacks.Already steeped in grief and shock, Germans were further rattled by news that a Syrian refugee had killed a 45-year-old Polish woman with a large kebab knife at a snack bar in the southwestern city of Reutlingen Sunday in what authorities called a personal dispute.