The British Foreign and Commonwealth Office said it was concerned about the safety of citizens in Turkey given the potential for political violence.
"Two major pro government rallies are due to take place in Ankara and Istanbul on June 15 and 16, respectively," a warning published Wednesday said. "There have also been reports that riot police have entered Istanbul's Taksim Square, a main focus point in the two-week-long demonstration."
Demonstrations over plans to raze a historic park in Istanbul have taken on a political tone amid ongoing protests.
The FCO warning said protests generally start midday. Demonstrations near tourist destinations have been generally peaceful so far, the advisory said.
The European Parliament expressed concern last week about the police reaction to the demonstrations. Tear gas and water cannons were used as riot control measures despite pledges by the Turkish government to use extraordinary measures as a last resort.
Members of the European Parliament said they'd vote on a resolution on the situation in Turkey following Wednesday meetings with EU foreign policy chief Catherine Ashton.