Conflict between security forces and Kurdish militants in south-east Turkey has spilled into sport, with football authorities punishing the region’s Amedspor club and banning one of its players for 12 matches for “ideological propaganda”.

Violence has flared since the collapse in July of a ceasefire between the army and Kurdish militants. Fighting that has killed more than 40,000 since 1984 has now spread into the streets of towns, many now under curfew.

Turkey’s football federation said on Thursday it had imposed a ban on the midfielder Deniz Naki and a 19,500-lira (£4,600) fine over “unsporting” comments made as second division Amedspor beat Bursaspor last week to win a place in the cup quarter-finals.

“We dedicate this victory as a gift to those who have lost their lives and those wounded in the repression in our land which has lasted for more than 50 days,” Naki, 26, wrote in a Facebook post after the match. “We as Amedspor have not bowed our heads and will not do so. We went on to the pitch with our belief in freedom and won,” said the Germany-born Kurdish player, whose parents come from Tunceli in eastern Turkey. He represented Germany at under-21 level.

The conflict in the south-east is hugely divisive, stirring up nationalist sentiment on both sides. It has also raised deep concern among Nato allies who fear it could obstruct collective action against Islamic State militants across Turkey’s borders in Syria and Iraq.

The ban on Naki came on top of a fine against Amedspor and a ruling that it play the cup quarter-final without spectators on 10 February as a result of “ugly and bad” chants by fans at a match last week, according to a federation ruling on Thursday.

“Everywhere is Sur, everywhere resistance,” Amedspor fans could be heard chanting in reference to the historic walled quarter of the city of Diyarbakir which has been under round-the-clock curfew since December.

An Amedspor representative, Ekrem Yesil, said the club would appeal against the rulings to Uefa among others. “These rulings are unjust,” he said. “A second division side is fighting for the cup and has been able to create a quality team. In football terms, it has come to an unacceptable point.”

The state says curfews have been imposed in the region to enable security forces to remove barricades, explosive devices and ditches set up by militants from the Kurdistan Workers’ Party (PKK), designated a terrorist group by Turkey, the United States and European Union.

The army says hundreds of militants have been killed, along with scores of security force members since the launch of concerted security operations in December. Pro-Kurdish politicians, who deny acting for the militants, say more than 100 civilians have died in the fighting and tens of thousands of residents have been forced to migrate.