Thai security forces and anti-government protesters remained in a stand-off in Bangkok after clashes overnight in which one person died.
Shots and bangs were heard overnight as security forces moved to cut power and seal off access to the large protest camp in the city centre.
Earlier, a renegade general supporting the protesters was shot by an unknown gunman and is in a critical condition.
The protesters want Prime Minister Abhisit Vejjajiva to step down.
Streets which would normally be full of commuters were almost empty early on Friday, says the BBC’s Vaudine England in Bangkok.
Thousands of protesters, known as red-shirts after the colour they favour, have reinforced their barricades and vowed to maintain their camp in a commercial district of Bangkok until elections are called.
"The total seal-off measure took place since yesterday evening," army spokesman Col Sunsern Kaewkumnerd said.
"Metropolitan Electricity Authority has cut off the power around Ratchaprasong intersection last night," he said.
The authorities have also begun to cut public transport and some mobile phone service to the area occupied by the protesters.
The government has threatened for days to cut off power, water and food supplies to the red-shirt camp but the protesters have their own supplies and appear ready for a long siege, says our correspondent.
Commander Red shot
Early on Friday, a new clash was reported as protesters apparently threw stones and bottles, prompting soldiers to fire warning shots in the air.
Overnight, one protester was shot dead after a group of red shirts confronted armed security personnel on the outskirts of the barricaded encampment.
At least nine people were reported to have been injured.
The clashes followed the wounding of a renegade Thai general who had been organising the red-shirts’ security.
Khattiya Sawasdipol, better known as Seh Daeng (Commander Red), was shot in the head and seriously injured.
Seh Daeng is part of the protesters’ more radical wing and had accused red-shirt leaders – many of whom have distanced themselves from him – of not being hard-line enough.
Circumstances surrounding the shooting, near the Silom business area, are not clear.
A spokesman for the red-shirt movement blamed an army sniper but military officials said troops had orders to fire only in self-defence.
The protesters – who have been occupying parts of Bangkok for more than two months – want Prime Minister Abhisit Vejjajiva to dissolve parliament and call fresh elections.
Their camp stretches from the city’s shopping district south to its business hub.
Mr Abhisit is under severe pressure to end the protests, which have paralysed Bangkok since 14 March.
He had offered polls on 14 November – but the two sides failed to agree a deal because of divisions over who should be held accountable for a deadly crackdown on protests last month.
The 10 April operation left 19 protesters, one journalist and five soldiers dead.
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