A potential threat to President Gloria Macapagal Arroyo's leadership ended peacefully Sunday night after disgruntled marine officers called off a five-hour standoff that started when their commander was relieved of his duties.

The standoff at marine headquarters showed that efforts to oust Arroyo remained alive two days after she imposed a state of emergency, saying a coup plan had been foiled but "treasonous" elements remained. Arroyo's critics fear the security clampdown is a step toward martial law.

Earlier on Sunday, the head of the marines, Maj. Gen. Renato Miranda, was removed from his post. The marines have been widely rumored to have been among military units involved in the coup plot.

After the announcement of Miranda's removal, Marine Col. Ariel Querubin said he was going to join his commander at their headquarters in suburban Manila. He urged people to defy a ban on rallies and turn out en masse to protect officers of the elite unit implicated in the foiled plot.

"I'm going to join him at the headquarters and then we'll ... wait for all the people to really come here and protect us," he said. Asked what they needed protection from, Querubin said: "From aggression."

But the standoff ended peacefully after only a few thousand supporters heeded his call. Riot police tried to intervene twice to disperse the demonstrators. But they resisted and police backed off each time, apparently on orders not to worsen the situation with violence.

Querubin was named by the military Friday as a key figure in plans by marine officers and their men to walk out and withdraw support for Arroyo. On Sunday, he confirmed the plan, claiming a majority of the force was ready to go when they found the camp sealed in a security clampdown.

"The junior officers are really raring, they're so agitated, so I told them to avoid clashes and shooting, let us just march," he said.

The 8,000-strong marines are regarded as an elite, well-armed unit at the front line of the government's war against Muslim and communist guerrillas and Al Qaeda-linked militants in the country's volatile south.

The U.S. Embassy said it was monitoring the situation carefully and called for a peaceful resolution of the crisis.

"We reiterate our call for the government of the Philippines and Armed Forces of the Philippines, the Filipino people to respect fully the rule of law, protect civil liberties, human rights and reject violence," embassy spokesman Matthew Lussonhop said.

Military spokesman Lt. Col. Tristan Kison said Miranda had been asked to be relieved as commander of the marines, citing personal reasons. Kison said Miranda has not been implicated in the coup plot. But other reports suggested he had been forced out.

Kison played down widespread rumors of unauthorized troop movements and disgruntled troops.

"Let us remain calm, there is no reason to panic," he said.

Miranda was replaced by his deputy, Brig. Gen. Nelson Aliaga, who took over in a brief ceremony in a military camp. He said all those involved in standoff had agreed to follow the chain of command.

Arroyo's decree on Friday set off an uproar as Filipinos celebrated the 20th anniversary of dictator Ferdinand Marcos' ouster in a "people power" revolt. Even some supporters questioned the move.

The decree bans rallies, allows arrests without warrants, permits the president to call in the military to intervene and lets her take over facilities — including media outlets — that may affect national security.

On Saturday, police arrested at least three vocal critics of Arroyo and raided a small newspaper critical of the president.

Local and international journalists expressed alarm over the raid on offices of The Daily Tribune. Police seized editorial materials and threatened to take over the paper. Officers were posted at the Tribune's door.

Troops have also been deployed outside two of the country's largest TV networks, ABS-CBN and GMA7, purportedly to protect them from possible attacks by coup plotters. A prominent political columnist was arrested at an anti-Arroyo protest, and some journalists have complained that they are being stalked by government intelligence agents.

Reporters Without Borders criticized the raid and accused Arroyo of declaring the state of emergency to crack down on her political opponents.

"We fear a wave of arrests and more closures of newspapers critical of the government," the Paris-based group said.

The National Union of Journalists of the Philippines called on journalists worldwide to support the Philippine media "in this dark hour" by sending protest messages to the government and its embassies.

Philippine editors and columnists met Sunday and planned to issue an editorial condemning the raid on the Tribune as an assault on press freedom.

The Tribune produced an issue Sunday featuring a strongly worded editorial vowing to continue to criticize Arroyo. "We will not be cowed," the editorial said.