Thousands of seasonal workers from Asia come to Sweden each summer to pick wild berries.

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Around 120 Chinese seasonal berry pickers in northern Sweden went on a 15-kilometre (9.3-mile) march overnight to Friday to protest their salaries, a local social services official said.

Thousands of seasonal workers from Asia, most of them from Thailand, come to Sweden each summer mainly to pick wild berries in the north under sometimes difficult working conditions.

"Last night, around 120 Chinese berry pickers sat down on the road to protest," Kerstin Asplund, who is in charge of social services in the northern municipality of Storuman, told AFP.

The protesters carried out their sit-in after hiking 15 kilometres, carrying signs reading "SOS" and "Help," near the wooded area where they had been asked to pick berries, some 160 kilometres from the Arctic Circle.

"It is difficult to know what they want exactly, since there is a language barrier, but we know they are asking for an increase in pay," Asplund said.

After their sit-in, monitored by police, the demonstrators were driven by bus to a public venue that had agreed to accommodate them.

"We have explained to their employer, a Chinese company, that it is their responsibility to take care of this. But they tell us they are not able to discuss with them, that they do not want to work," Asplund said.

The demonstrators are part of a group of 200 Chinese berry pickers who arrived in Sweden's isolated northern region in recent days.

After a disastrous season last year sent many of the foreign berry pickers home weighed down by debt instead of profits, they have this year for the first time been provided with contracts guaranteeing them a monthly wage of at least 16,372 kronor (1,745 euros, 2,321 dollars).

Some Swedish unions however say the minimum salary is insufficient, pointing out that it in some cases is hardly enough to cover the money the workers have to shell out for things like plane tickets, housing and car rental.