Ayse Gokkan of the pro-Kurdish People's Democracy Party (BDP), who has been on hunger strike for seven days, said on Tuesday that the wall will divide the Kurdish people and has called it a "black stain on history."
The government has denied it is building a "fully-fledged wall" but local sources said construction began last month in the town of Nusaybin in Turkey's Kurdish-dominated southeast.
The move reflects Ankara's growing fears of a spillover of the Syrian conflict along the 910 kilometer (560 mile) border, they said.
Nusaybin faces the northeastern Syrian town of Qamishli, which has seen clashes between terrorist militants and Kurdish fighters.
But Gokkan, whose town has a large Kurdish population many of whom have relatives on the other side of the border, said the barrier would divide people.
"This is a wall of shame being built in the 21st century," she said, speaking through a press advisor.
Gokkan, who is conducting her hunger strike in an open mine field near the border checkpoint, said it was "unacceptable to build a wall of shame between the Kurdish people.
"Like the Berlin wall, this wall will remain a black stain on the history of mankind," she added.
Deputy Prime Minister Bulent Arinc said Monday authorities were only placing barbed wire over an existing structure to enhance security and insisted that a wall was "out of the question".
But local sources said an iron structure had already gone up and was now being filled with concrete.
The construction has fired local tensions -- on Sunday police fired tear gas against protesters who threw stones and Molotov cocktails in the town of Cizre near the Syrian border, injuring three police officers, security sources said.
Once a close ally of Syria, Turkey has cut off ties with the government in Damascus since the unrest began in March 2011 and has become one of the most fervent supporters of the militants in Syria.
The long Turkish-Syrian border has become increasingly tense and at least a dozen Turks have been killed by stray gunfire from the Syrian side.
Since then, the Turkish military has retaliated in kind for every Syrian shell that has landed on its soil.
Ankara has so far taken in more than 600,000 Syrian refugees fleeing the war in its neighbor and has occasionally closed border crossings for security reasons although it has maintained an "open-door" policy since the start of the conflict.
Turkish authorities have seized a large quantity of chemicals from a convoy trying to illegally enter the country from Syria, which "could be transformed into weapons", the army said Sunday.
Gokkan, who is demanding a halt to construction, has not eaten for seven days and is drinking little water, said her advisor, who asked not to be named. She is regularly checked by doctors.
"The mayor is very determined and will not stop the protest unless the project is dropped," said the advisor.
BA/BA