Two officers were killed and five wounded on a highway outside the city of Sirnak in a car bomb attack carried out by the outlawed Kurdistan Workers Party (PKK), the sources told AFP.
Security forces in assault helicopters then pursued the militants suspected of carrying out the attack. Five "terrorists" were killed, the office of the regional governor said.
Meanwhile, one policeman died and one more was wounded in a rocket attack carried out by the PKK in the Silvan district of the southeastern region of Diyarbakir.
Since late July, Ankara has used air power and ground forces in a self-declared "anti-terror" operation to try to cripple the PKK in its strongholds in southeastern Turkey and northern Iraq.
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But the group has hit back, killing dozens of Turkish police and soldiers in almost daily attacks.
The security forces had over the last week carried out a massive military operation against suspected PKK militants in the southeastern town of Cizre, lifting a curfew yesterday after nine days.
The authorities today imposed a curfew in several districts of Silvan after the deadly attack on police, informing citizens of the measure through loudspeakers on mosques, Turkish media said.
A curfew meanwhile was also imposed in parts of the central Sur district of Diyarbakir city, as the authorities conducted a new operation against suspected Kurdish militants.
A statement from the local governor's office said that the curfew had been put in place at 5:00 AM (0730 IST) and would last until further notice.
"We call on all the parties to take into account the public's expectations," he said in televised comments.