A 15-year-old asylum seeker living in a refugee centre in Sweden has been arrested on suspicion of murder after an employee at the shelter was fatally stabbed.

Alexandra Mezher, 22, was attacked at around 8am on Monday morning, at a centre for unaccompanied migrant children aged between 14 and 17 in Molndal, on Sweden's west coast.

She was taken to Sahlgrenska Hospital but later died of her injuries.

The incident as a number of young girls said they had been sexually assaulted by young male asylum seekers at a public swimming pool in central Stockholm - while police have warned the city's train station is 'overrun' by gangs of young, male migrants who are stealing and 'groping' women.

Sources say the 15-year-old boy was held down by other employees at the centre until police arrived.

Officers discovered a knife at the scene and cordoned off the area as they launched a murder investigation.

Miss Mezher, whose family are originally from Lebanon, had only worked at the accommodation for unaccompanied refugee children for a few months.

Her cousin described Miss Mezher as 'an angel' and told Swedish media: 'It is so terrible. She was a person who wanted to do good, who wanted to be good.

'And then he murdered her when she was doing her job. We have cried a lot. She was such a nice person, warm and happy.'

She added: 'It is the Swedish politicians' fault that she is dead.'

The stabbing comes on the same day as police in Sweden demanded more resources to stem rising violence linked to the migrant crisis.

Police spokesman Thomas Fuxborg said the assailant was a young man who was living at the centre, and confirmed the young man has been arrested on suspicion of murder.

He did not give details about the suspect's nationality but added the motive was not immediately clear.

Mr Fuxborg said: 'These kinds of calls are becoming more and more common.

'We're dealing with more incidents like these since the arrival of so many more refugees from abroad.'

Tensions are rising in Sweden and the country is struggling to cope with a record influx of migrants and asylum seekers.

The attack also came as National Police Commissioner Dan Eliasson requested 4,100 additional officers and support staff to help fight against terrorism, carry out migrant deportations and police asylum facilities.

He said: 'We are forced to respond to many disturbances in asylum reception centres. In some places, this takes significant police resources.

'This was not the case six months ago and it means that we won't be able to respond as effectively in other areas.'

According to the Swedish Migration Agency, the number of threats and violent incidents at asylum facilities more than doubled between 2014 and 2015.

In 2014, there were 148 incidents but in 2015 that number jumped to 322.

Meanwhile arson attacks targeting asylum shelters have also surged, with at least two dozen centres reduced to ashes or damaged by fire last year.

Also weighing on police resources are border controls introduced on January 4 and a higher national terrorist threat level after the Paris attacks in November.

'Many of the problems we are now facing help to prove the point that Swedish police have long been underfunded and under-staffed,' police union director Lena Nitz, told TT.

'It is obvious that the migrant situation is a great strain. It has become clear that the situation is completely unsustainable.'

The police request for more resources comes greater attention is being focused on allegations of violence by young migrants across Europe, with some countries expressing doubt about their ability to integrate them into society.

Like the rest of Europe, Sweden has been struggling with the continent's biggest migration crisis since World War II.

A country of 9.8 million, Sweden took in more than 160,000 asylum seekers in 2015, putting it among the EU states with the highest proportion of refugees per capita.

It has since tightened its asylum rules to curb the migrant flow.

MailOnline reported that a number of girls have reportedly been sexually assaulted by young male asylum seekers at a public swimming pool in central Stockholm.

The alleged perpetrators are all 'unaccompanied minors' - young refugee boys who have arrived in Sweden seeking asylum without a parent or guardian.

The four cases involve girls under the age of 18 and all sexual assaults have taken place in hot tubs, pools or in the changing rooms if Eriksdalsbadet, Stockholm, in the past three weeks.

Eriksdalsbadet, which is the biggest aquatics centre in Stockholm, has previously reported an spike in sexual assaults - mainly incidents involving boys and young men groping women.

At the same time Swedish police have warned that Stockholm's main train station has become unsafe after being 'taken over' by dozens of Moroccan street children.

The all-male migrant teen gangs are spreading terror in the centre of the Swedish capital, stealing, groping girls and assaulting security guards, according to Stockholm police.

Members of the gangs, some as young as nine, roam central Stockholm day and night, refusing help provided by the Swedish authorities.