By James Pomfret

WUKAN, China (Reuters) - The Chinese fishing village of Wukan staged a fourth straight day of protests on Wednesday against what residents say was the unlawful arrest of the village chief, a rare show of grassroots defiance against authorities in Communist China.

Wukan, in the southern province of Guangdong, made international headlines in 2011 as a symbol of grassroots democracy after an uprising against corrupt local authorities and illegal land grabs that resulted in rare concessions being granted by provincial Communist Party leaders.

Under a blazing sun, the village of 15,000 once again united to march for the release of Lin Zuluan, the popular and democratically elected village chief who was arrested in a surprise midnight raid over the weekend.

Lin was shown on state television on Tuesday confessing to accepting bribes, but many villagers profess his innocence, saying he'd been forced into making a confession.

Sources close to the Lin family said his grandson was detained by police soon after Lin's arrest and interrogated for 12 hours.

The grandson was released soon after Lin's confession went public, they said.

Despite repeated warnings by authorities to the villagers not to stir up trouble, more than a thousand again marched in a loud procession, waving red China flags and chanting for justice.

"The villagers of Wukan don't believe Lin Zuluan took bribes," read a hand-written white banner held up by a group of several children at the vanguard of the procession.

They also held up banners making a broader appeal to national leaders in Beijing to "save Wukan".

"We want the central government to come and investigate," said Wei Yonghan, an elderly villager joining the march.

"We won't give up. We'll keep marching every day till they listen to us."

Wukan's defiance in 2011 took place during the administration of former president Hu Jintao. It remains unclear whether security forces will take a stronger line under President Xi Jinping who has cracked down on rights activists across China since taking office.

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Over the past few days, however, authorities seem to have tightened their grip. Some reporters were warned by authorities in nearby Shanwei of "inciting, planning and directing the protests," according to reports carried in Chinese state media.

Foreign media outlets including Reuters were urged to leave the village immediately.

A villager who was taken into detention by police and interrogated said authorities were aggressively going after potential ringleaders of the protests to quash any escalation of unrest.

"They questioned me for hours and wanted to know everything, who was organizing things," the villager, who declined to be identified, said. "They told me to open my Wechat (messaging app) ... and spent hours looking through my messages."

While there didn't appear to be a mass deployment of riot police for the protests on Wednesday, at least three drones could be seen hovering in the sky tracking the demonstration.

Villagers also occasionally chased off individuals in the crowds they believed to be plain-clothes officers.

The village is about a four-hour drive east of Chinese-ruled Hong Kong, where months of pro-democracy protests brought chaos to the streets in late 2014.

(Editing by Nick Macfie)