The leader of Turkey's main opposition party has visited a party lawmaker whose imprisonment inspired a 25-day protest march.

Enis Berberoglu was sentenced to 25 years in prison last month for allegedly leaking footage to an opposition newspaper suggesting Turkey smuggled arms to Islamist rebels in Syria.

Kemal Kilicdaroglu, the Republican People's Party's leader, told reporters outside an Istanbul prison on Monday that "justice has been convicted and jailed." He says jailing people "unjustly" would create "deep wounds" in society.

The party leader marched 450 kilometers (280 miles) and was joined by tens of thousands in what grew into a protest of the massive government crackdown following last summer's failed coup.