Militants from the separatist Kurdistan Workers' Party, known by its Kurdish initials PKK, launched coordinated attacks on police checkpoints in Sirnak.
Turkish newspaper Today's Zaman reports that one policeman was killed and three others were injured. Security forces responded to militants armed with rocket launchers, killing eight PKK fighters.
"A large-scale operation was launched by special operation police officers and gendarmes against the terrorist group following the incidents," the report adds.
In Ankara, security forces clashed with demonstrators during celebrations for Republic Day, a commemoration of the founding of the Turkish republic in 1923.
Today's Zaman reports that security forces were on alert after protest permits were denied for more than 30 opposition groups in the country. Some groups, authorities in Ankara said, "may seek to incite anarchy in the country."
Kemal Kilicdaroglu, leader of the opposition Republican People's Party, was said to have been overcome by tear gas during Monday's demonstrations.
More than 3,000 police were deployed to Ankara ahead of the protests.