By Nick Thorpe
BBC News, Pristina
Serbs have turned against those who recognise the new Kosovo
One week since the declaration of independence, Serb authorities in north-western Kosovo are pushing hard to eradicate all institutions with any connection to the new state.
And they are telling a cautious and already weakened UN mission, in its last months in office, that it should allow this - or face dire consequences.
There is genuine Serb grief over the loss of Kosovo, but there is also a carefully calibrated plan to win important parts of it back, and to sabotage Kosovo as an independent state.
The tools available include violence against property - grenades thrown at UN, EU, and Kosovan justice ministry buildings, and the carefully planned and executed burning down of two border and customs posts on 19 February.
Privately, Serb leaders in the north say this is just the beginning.
United Serb front
The UN Mission in Kosovo (UNMIK) is awaiting instructions from the UN secretary general in New York, and from the so-called "Contact Group" - the US, UK, Germany, France, Russia, the European Commission - as well as the new EU mission in Kosovo, the International Civilian Office (ICO).
The aim is to portray Kosovo as a state of criminals
Minister for Kosovo,
UNMIK is hesitating. The line from New York is that the UN is "status-neutral" - neither recognising nor opposing an independent Kosovo.
Serbs in the north-west say they have nothing against UNMIK continuing its work there - provided it does nothing to nurture or protect Kosovan institutions.
A united Serb front, made up of hard-line Serb leaders, is trying to dictate policy to the UN.
As in Croatia and Bosnia in the 1990s, the UN is caught on the horns of a dilemma - whether or not to stand up to radical Serb nationalism. The precedents are not good.
What is different about Serb nationalism today, compared with the 1990s, is that for the moment its enemy is not the other nations of the Balkans.
The enemy is instead those countries which recognise an independent Kosovo.
Police were not guarding the US embassy at the time of the attack
The attacks on foreign embassies in Belgrade and on UN property in Kosovo confirm this.
There are several thousand ethnic Albanians and other minorities living among about 40,000 Serbs in northern Kosovo.
Buses still run each day, with a police escort, taking them to work places and schools in the south.
Some also cross by a footbridge over the River Ibar. Despite the growth in tension in the north, there have been no atrocities against them.
The following are points of contention:
Serb leaders say they will not tolerate their continued operation, as the institutions of a sovereign state.
Northern Kosovo is a haven for organised crime and smuggling
Slobodan Samardzic, the minister for Kosovo in the Serbian government, described their destruction this week by mobs as "legitimate".
Serbian Prime Minister Vojislav Kostunica is not sponsoring paramilitaries today, as the government did during the 1990s, but they are sponsoring violence against UN and Kosovan government property.
Interestingly, Serbian customs posts just across the border were also torched.
Northern Kosovo is a haven for organised crime, with no number plates on cars, and major smuggling operations.
"The aim is to portray Kosovo as a state of criminals," Mr Samardzic says.
The Kosovo Police Service (KPS)
The KPS is 7,200-strong and multi-ethnic. About 10% of its officers are Serbs.
The River Ibar could form a new frontier between Serbia and Kosovo
In much of the country, there are still multi-ethnic patrols, but no longer in the north-west. Albanian KPS officers have been withdrawn for safety reasons.
Serb KPS officers are under huge pressure from hard-liners, with threats to their homes and family members.
They remain in uniform, but warn they will quit if forced to take orders from KPS commanders in Pristina. They now only accept orders from UNMIK police.
The court and prison in Mitrovica
The Serbs are demanding that Albanian staff who normally work there should not be allowed to return.
If independence is undermined, a violent Albanian response would become more likely
There are daily demonstrations by pre-1999 staff demanding their jobs back.
They say they will only accept UNMIK control, not Pristina control.
The International Civilian Office
The ICO building is close to the main KPS police station in northern Mitrovica. The Serbs say they will not tolerate it.
The International Civilian Representative, Pieter Feith, has advocated a gradual approach to winning over such implacable opposition.
The new EU mission in Kosovo has not been welcomed by Serbs
But he has also hinted that Belgrade's progress towards the EU might in future become conditional on how they and the Kosovan Serbs treat the EU mission.
This is the dilemma facing UNMIK - if they stand firm, and call in Nato ground support, they will lose their neutral status and become parties to the conflict.
If they cave in, the Serbs will have achieved the de facto partition of Kosovo, along the line of the Ibar.
If that is then combined with the strengthened operation of parallel Serb institutions in enclaves elsewhere in Kosovo, Kosovan independence would then begin to look very patchy indeed.
If independence is undermined, a violent Albanian response would become more likely.
This may also be the Belgrade government's hope, as this would discredit Pristina's position in the eyes of the international community.