Police in Finland have arrested an 18-year-old man suspected of killing two people and wounding seven others early Saturday.

The body of a shooting victim lies covered with a sheet following multiple shootings by a gunman in Hyvinkaa in southern Finland.

The gunman had opened fire at 1:53am local time from a rooftop in the centre of Hyvinkaa, a town of 45,000 located 56 kilometres north of Helsinki, killing an 18-year-old woman, local police said.

He also wounded eight others, including an 18-year-old man who later died in hospital, according to the Finnish news agency FNB which quoted police.

The injured include a 23-year-old policewoman who was in critical condition. The killer took aim at people outside local bars, according to a statement on the police website.

Police did not identify the suspect, but said he was dressed in camouflage fatigues. He did not have any previous criminal record, nor did he resist his arrest near Hyvinkaa.

Police seized two rifles but said the suspect did not have any gun permits.

"We have no indication that the suspect was in any way connected with the people," said Satu Koivu, superintendent of the Central Uusimaa police department.

Finland has had three mass shootings since 2007. The popularity of hunting means that gun ownership is widespread. There are about 1.6 million guns and more than 670,000 firearm licences in the country of 5.4 million people, according to the Interior Ministry. Finnish gun laws were tightened in June.

Twenty Finns died in two gun attacks at schools in 2007 and 2008, including the assailants, who shot themselves. Six people, including the gunman, were killed in a shooting at a shopping mall in the Helsinki area on New Year’s Eve in 2009.