MANILA - The country's largest Moro rebel group denied Tuesday that it resorted to intimidation and vote buying to influence a plebiscite on the ratification of a law that will expand the autonomous Muslim region.

Cotabato Mayor Cynthia Guiani-Sayadi claimed that voters were scared off when "thousands" of Moro Islamic Liberation Front (MILF) members trooped to her city during Monday's poll on whether or not to ratify the Bangsamoro Organic Law.

MILF identification cards were also confiscated from an underage flying voter. Several companions of the teenager evaded the residents who chased them, she said.

• Scuffles erupt in Cotabato poll precinct on Bangsamoro plebiscite day

On the eve of the plebiscite, a grenade also exploded outside the house of Judge Rosalito Rasalan, a critic of the Bangsamoro law. The judge previously received threats on social media, said Sayadi.

"This is something that affected the credibility of the election... It was marred by violence, intimidation, vote buying," the mayor, who opposes the Bangsamoro law, told ANC.

Watch more in iWantv or TFC.tv

MILF chair for political affairs Ghazali Jaafar said his group lacks funds to buy votes.

"Some" MILF members went to Cotabato on Monday, but only for sightseeing in the sultanate government's former seat of power, he said.

"We don't believe in intimidation," Jaafar said in the same ANC interview.

"We want Cotabato to join the Bangsamoro government; that is correct, we cannot deny that... [But] we want it to be a member of the Bangsamoro government through a democratic way because we believe in a democracy," he added.

He said it was also his first time to hear of Judge Rasalan.

Police and the Commission on Elections should nonetheless look into Sayadi's allegations, he said.

The mayor said she will file a case against those involved in the incident.

Asked if she will also question the poll results, the mayor did not answer directly and instead noted that Comelec Commissioner Sheriff Abas has ties to the MILF.

Abas is the nephew of MILF chief negotiator Mohagher Iqbal.

The Bangsamoro law is the product of a 2014 peace deal between the government and the MILF, which has sought self-governance for the Moro people since the 1970s.

Under the measure, Bangsamoro will get $950 million in development funds over the next 10 years, as well as a chunk of the tax revenue generated within its borders.

The national government will keep control over the police, though the leadership of the autonomous area will be closely involved in security matters.

Final results are expected to be released within 4 days of the voting, with an approval triggering the demobilization of a third of MILF's fighters, which it says number 30,000.

Muslim rebels have long been battling for independence or autonomy on Mindanao, which they regard as their ancestral homeland dating back to when Arab traders arrived there in the 13th century.

With a report from Agence France-Presse