FERGUSON (REUTERS, AFP) - Police said Wednesday they had arrested 47 people during a night of protests in Ferguson, the Missouri town rocked by violence over the police shooting of an unarmed black teenager.

Captain Ron Johnson of the Missouri Highway Patrol said protesters threw bottles of water and urine at police towards the end of Tuesday night's protest, prompting officers to intervene after an otherwise peaceful night.

"As of 1:00 am we have 47 arrests," he told a press conference, adding that police had also seized three guns from demonstrators.

Capt Johnson stressed that unlike a protest Monday night, protesters did not fire guns at police and police refrained from using tear gas to break up the rally.

"Tonight we saw a different dynamic," he said.

Protests in the town of 21,000, a predominantly African-American suburb of St. Louis, have been punctuated by looting, vandalism and clashes between demonstrators and police every night since Michael Brown, an unarmed 18-year-old, was killed by a white police officer on Aug. 9.

Community leaders, politicians and city officials had redoubled their appeals for order on Tuesday, calling for citizens to stay off the streets after sunset, even though a mandatory curfew had been lifted.

In the hours after darkness fell, protesters were notably fewer in number and more subdued than on previous nights. Onlookers milled about as civic activists, members of the clergy and even Missouri Attorney General Chris Koster mingled with demonstrators.

But as the rally was winding down and most of the protesters were leaving the area, someone among the dozens still in the streets hurled a plastic water bottle at police.

Helmeted officers, some with heavy weapons and dogs, suddenly emerged in force. They ordered the remaining protesters to leave and chased down those who resisted as more bottles were thrown. Several demonstrators were seen being led away in handcuffs.

The confrontation capped an otherwise mostly peaceful night of demonstrations, the most tranquil in Ferguson since last Thursday, when a state Highway Patrol captain was placed in command after the local police force was widely criticized for heavy-handed tactics.

The Brown case was due to take a new turn on Wednesday, when the St. Louis County prosecutor's office was expected to begin presenting evidence to a grand jury investigating the shooting. The officer who shot Brown, Darren Wilson, has been placed on leave and went into hiding as Brown's family and supporters called for his arrest.

US Attorney General Eric Holder was slated to visit Ferguson on Wednesday to be briefed on a separate civil rights investigation he ordered into the slaying.