Sweden’s chief of police has promised to increase the number of officers on the ground in the southern city of Malmö during what he called “troubled times.” The announcement comes just three days after the latest grenade attack in a city that has already seen 30 explosions so far this year – up from 25 in 2014.

On a visit to the city on Thursday, Sweden’s police chief Dan Eliasson said hundreds of extra officers would be sent there after months of shootings, stabbing and explosions. Exacerbating matters, up to two thirds of the city’s police are reported to be on holiday, with concerns the public is being put at risk.

Eliasson said the southern city was in “troubled times now, so I want to see an increased presence and visibility.” He denied the grenade attacks were terror related: “other stuff is behind [the attacks],” he said. “There are very sprawling motives – it is about drugs, in some cases, or for revenge for historical injustice,” he told local newspaper Sydsvenskan.

“Police in the south is the prioritised area and will receive most of the new police officers in 2015 and 2016. At the moment, slightly more than 90 officers [are being appointed], in January just above 100, and in summer 2016 there will be further additional staff, but the figure has not been determined yet.

“All of the Swedish police force’s resources are available to them. We have already reinforced Malmö with staff for the acute situation, but if more is needed I am prepared to make those decisions. It could be reconnaissance resources, investigators, bomb technicians, helicopters, anything.”

Only hours after the announcement was made, police were scrambled to a number of car fires in the city. A gang of men was spotted breaking into vehicles and setting them ablaze in one area, followed shortly after by two more cars catching fire in a different district, The Local reports.

Sweden’s recent response to the violence has been to stop knifes being sold near where stabbings have occurred and increase security for asylum seekers. They, rather than the “ordinary shoppers” who are under attack, were prioritised because “dark forces in society” could react to the wave of migrant violence – as one police spokesman put it.

Sweden now attracts more asylum seekers than any other nation in Europe bar Germany – applications have increased by 140 per cent since last year. Just before 7am today an illegal migrant was discovered in the luggage bay of a plane from Ethiopia.