Image copyright AFP Image caption Police used pepper spray on some protesters at the sit-in

US police have arrested at least 17 people in the city of St Louis, Missouri, during a weekend of planned protests against police shootings.

Demonstrators were held for unlawful assembly after staging a sit-in outside a convenience store early on Sunday.

Thousands have taken part in rallies and vigils as part of a four-day event named Ferguson October.

Weeks of protests have been sparked by the killing of unarmed black teenager Michael Brown in nearby Ferguson.

Several demonstrators gathered outside a QuikTrip petrol station and convenience store in St Louis on Sunday morning, refusing to disperse.

Image copyright AFP Image caption Demonstrators and police gathered outside a QuikTrip store early on Sunday

Image copyright AP Image caption The protesters locked hands and refused to disperse

Riot police used pepper spray to clear the protest.

St Louis police chief Sam Dotson said on his Twitter account that the protesters were "attempting to storm" the store and had thrown rocks at police officers.

Protesters denied throwing rocks at the police.

A QuikTrip store in Ferguson was wrecked during violent protests in the aftermath of Michael Brown's killing, and later became a gathering point for protesters.

Image copyright AP Image caption Police say rocks were thrown by the protesters

Tensions in St Louis are also high after another black teenager, Vonderrit D Myers, was shot dead by a police officer on Wednesday.

Police said 18-year-old Myers shot at an officer, but the victim's parents say he was unarmed and racially profiled.

'Civil disobedience'

Ferguson October began on Friday, when hundreds of demonstrators lined up outside the office of the local prosecutor, Robert McCulloch.

Demonstrators chanted slogans calling for Mr McCulloch to charge Darren Wilson, the officer who shot Mr Brown in August.

On Saturday, there was a peaceful march through the centre of St Louis to the Keiner Plaza park. The crowd was larger than the day before, according to the Associated Press.

"This isn't going to stop until there is change with police and black youth," Tory Russell, one of the protest organisers, said.

Image copyright AP Image caption Concerts and marches have been held as part of Ferguson October

Image copyright Reuters Image caption A woman signs a memorial for Vonderrit D Myers, who was shot last week

Protest organisers said the weekend of events was intended "to build momentum for a nationwide movement against police violence".

"We are here to bring peace, to bring restoration, to lift our banners in the name of those who've been sacrificed," said another protest organiser, Montague Simmons.

Planned events include street protests as well as a music event and a day of "civil disobedience".

Organisers have urged people from across the US to attend.

A US justice department investigation into the shooting of Michael Brown in August is continuing.