Turkish police Sunday blocked the entrance to Istanbul's Gezi Park, the epicentre of anti-government protests in June, to prevent a demonstration against a possible military intervention in Syria.
Riot police advanced with shields but held back from using tear gas or water cannon against about 1,000 activists who instead formed a human chain on the city's celebrated Istiklal Avenue, according to an AFP photographer who witnessed the scene.
"United States, killers, stay out of Syria," shouted protesters, who are firmly opposed to Ankara's support for proposed US-led air strikes against the regime of Syrian President Bashar Al-Assad.
Smaller human chains were formed in neighbourhoods across Istanbul, with many protests organised by the same groups who had occupied the park to fight against its commercial development.
June's unrest erupted when a peaceful sit-in on May 31 was met with a heavy-handed response that left at least five dead and thousands injured in three weeks of clashes between protesters and police.
The violence spiralled into nationwide demos against Turkish Prime Minister Recep Tayyip Erdogan and his ruling Justice and Development party (AKP), accused of repressing critics and of forcing Islamic values on the mainly Muslim but staunchly secular nation.
There were also further protests across Turkey against military action in Syria.
In the southern Turkish town of Antakya, close to the Syrian border, which has a large Alawite community, the same faith shared by Assad, some 2,000 people on Sunday protested their opposition to any military intervention in Syria.
"No to war, resistance, Syria! Greetings to the Syrian people who do not bend to imperialism!" chanted the demonstrators, according to an AFP photographer at the scene.
Up to 30,000 people protested in Diyarbakir, the main city in the south-east Anatolia, where the majority of the population is Kurdish. They called on the Turkish government to revive the peace process as fighting flares in Syria between Kurds and Islamists.
"The mother language is a right, it is not negotiable," they chanted, demanding education in Kurdish.
They also called on Turkey to open its borders held by Syrian Kurds for humanitarian aid.
Protesters also waved pictures of Abdullah Ocalan, the imprisoned rebel Kurd leader.
Ocalan has been in negotiations since late 2012 with the Turkish authorities for an end to the Kurdish conflict, which has cost some 45,000 lives since 1984.