The mayor of Oslo has warned that drug smugglers are increasingly targeting the Norwegian capital as a gateway to Europe as authorities tighten controls on major ports such as Antwerp.

Oslo’s mayor, Anne Lindboe, said drugs worth up to £570m have been smuggled through Norway’s largest port, which receives 50-70 ships and 243,000 containers every week.

“It seems that the port of Oslo is becoming a preferred port in Europe for criminal, hardened gangs,” Lindboe told the broadcaster NRK. Oslo port, she added, was “slightly too poorly guarded”.

Earlier this month, customs officials in Antwerp, the European capital of drug smuggling, said cocaine seizures in the Belgian port were down by half as criminal gangs switched routes to evade detection after an increase in policing.

In Oslo, however, there are concerns that security is not tight enough. The Norwegian customs union says it has only one mobile scanner at Oslo, which is shared with two other ports. When it is not available, customs officers have to check containers with handheld scanners, which they say are not as effective.

Calling for action, the union leader Karin Tanderø Schaug said the situation in terms of cocaine and organised crime was “critical” and that it was essential to “reinforce the customs in Norway”.

“This fight [across Europe] is so important. We cannot afford to underestimate the importance of control at the borders,” she added.

Among young adults, Norway has the third highest cocaine consumption in Europe. Last year, the Norwegian customs service made 1,847 drug seizures – more than in the previous 10 years combined – including record quantities of cocaine.

The amount of cocaine in Oslo is “alarming and increasing”, said Tanderø Schaug, urging the Norwegian government to act. “When Antwerp [has] more control and police, the criminals will change routes. And Norway can easily become a transit country as well. Same for Sweden.”

The Norwegian government has proposed increasing funding for the customs service to strengthen its efforts against drug trafficking.

The finance minister, Trygve Slagsvold Vedum, said: “Drug trafficking and organised crime is a threat to our society. To stop the gangs, we must confiscate their money and stop the flow of drugs into Norway. We are aware that Oslo is one of the ports used for importing illegal drugs, which is why there is a scanner that can be used at both ports in Oslo as needed, according to the customs agency’s threat assessments.”