* Complex coalition talks seen after close election result
* Sense of insecurity sways many voters
* Nationalists rebound on climate change, migration fears (Recasts with final results)
By Anne Kauranen and Tarmo Virki
HELSINKI, April 14 (Reuters) - Finland's leftist Social Democrats and the nationalist Finns Party emerged nearly tied to win Sunday's general election, reflecting a mounting sense of insecurity in the Nordic nation over immigration, welfare and climate change.
Tipped to win, the opposition Social Democrats scored 17.7 percent, while their eurosceptic Finns Party rivals were at 17.5 percent, according to final results from the justice ministry.
The co-ruling Centre Party of Prime Minister Juha Sipila and centre-right National Coalition stood at 13.8 percent and 17.0 percent, respectively, marking the first time in a century that no party won more than 20 percent in a general election.
With a fragmented parliament and deep divisions within the mainstream parties over how to tackle rising costs of expensive public services, coalition talks following the election could be protracted.
But Social Democrat leader Antti Rinne, 56, a former union boss, was expected to have the first shot at forming a government, with most party leaders having ruled out cooperation with the populist Finns.
"For the first time since 1999 we are the largest party in Finland ... SDP is the prime minister's party," Rinne told supporters and party members celebrating in central Helsinki.
With the European Parliament election less than two months away, the Finnish ballot is being watched in Brussels.
Underscoring a growing confidence among the far-right in Europe, anti-immigration parties, including the Finns, have announced plans to join forces after the May 26 EU election in a move that could give them a major say in how the continent is run.
At stake in Finland is the future shape of the country's welfare system, a pillar of the social model across the Nordics, which the leftists want to preserve through tax hikes and the centre-right wants to see streamlined because of rising costs.
Just as the Social Democrats are benefiting from a growing sense of insecurity among Finland's older and poorer voters, the Finns argue that the nation has gone too far in addressing issues such as climate change and migration at its own expense.
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After losing some ground when hardliner Jussi Halla-aho took the party's reigns in 2017, the Finns have made rapid gains in recent months when a number of cases of sexual abuse of minors by foreign men stirred anti-immigration sentiments.