Rioting has broken out in Belfast in the latest violence to flare up in Northern Ireland over a decision by councillors not to fly the British flag all year round.
Tensions have risen in the British province since Belfast's council voted on Monday to limit the number of days the Union Jack can fly over the City Hall to 17, outraging loyalists who believe Northern Ireland should retain strong links to Britain.
Two police officers were injured - one of them hospitalised - during clashes close to the city centre on Friday night, the Police Service of Northern Ireland (PSNI) said.
Two cars were set alight while eyewitnesses said protesters hurled stones, bricks and bottles at the police.
A PSNI spokeswoman said the force was dealing with "minor disturbances" in Belfast.
Loyalists have held nightly protests in several parts of Northern Ireland since Monday's ruling and there are plans for a major demonstration in central Belfast on Saturday.
A Belfast member of parliament, Naomi Long, received a death threat on Friday for her non-sectarian Alliance party's support for the change in flag policy.
Two bombs were also found in other parts of Northern Ireland in a sign of the lingering sectarian tensions despite the peace process, which largely ended three decades of sectarian violence in the 1990s.
The fresh unrest came after US Secretary of State Hillary Clinton visited Northern Ireland on Friday, winning praise from the province's leaders for her role in helping to build peace.
First Minister Peter Robinson and his deputy Martin McGuinness praised Clinton and her husband, former US president Bill Clinton, for their steadfast support when loyalists and republicans grappled to end the bloodshed.
"Both Hillary and Bill Clinton have been absolutely vital voices for us in our process and that is something that has to be recognised, over many, many years," McGuinness told reporters after their talks.
Some 3500 people died in the three decades of violence between Northern Irish Protestants who favoured continued union with Britain, and Catholics seeking a unified Ireland.
A 1998 peace agreement largely ended the conflict, but sporadic unrest and bomb threats continue as dissident offshoots remain violently opposed to the power-sharing government in Belfast, formed of Catholic and Protestant parties.