* Protesters urge backers to confront forces in rural areas
* Abhisit says scaling back economic growth projections
* Army chief admits divisions in forces but says not unusual (Recasts, adds second blockade and red-shirt comment)
By Jason Szep
BANGKOK, April 25 (Reuters) - Anti-government protesters encamped for weeks in central Bangkok promised more aggressive measures after the government rejected their proposals to end increasingly violent protests in return for early polls.
"Red-shirt" protest leaders called on their supporters in the countryside to confront the army and police. Their backers responded by blockading police convoys in at least two areas.
The stalemate rekindled fears of more unrest and a heavier toll on Southeast Asia's second-biggest economy as more retailers shut their doors and tourist numbers dwindle.
Prime Minister Abhisit Vejjajiva said he would soon scale back Thailand's annual economic growth forecast.
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About 500 km (310 miles) north of Bangkok, hundreds of "red shirts" formed a roadblock in northeastern Udon Thani province and stopped a convoy of 150 police from heading to the capital to strengthen security operations, a local official told Reuters.
They formed another roadblock in Pathum Thani, about 50 kms (30 miles) north of Bangkok, preventing around 200 policemen from entering the city.
Police reinforcements are being brought into the capital to forcibly disperse thousands of protesters occupying some central areas, said red shirt leader Jatuporn Prompang.
"We will try to block every spot we can in a bid to stop killing. We don't want to see anybody die," he told Reuters.
The army's failed attempt to eject red shirts from another site in Bangkok on April 10 led to clashes that killed 25 and wounded more than 800.
Coming after red shirts stopped a troop train in the north last week, the blockade raises questions over whether Abhisit can exert full control over rebellious parts of Thailand as the deadly protests enter a seventh week.
SOLIDARITY WITH MILITARY
Abhisit, speaking on Sunday in a televised interview with army chief Anupong Paochinda in a show of solidarity with the military, flatly rejected a red shirt offer to call elections in 30 days and hold a vote 60 days later.
"There must not be a precedent that allows intimidation to bring about political change," Abhisit said in his weekly television broadcast on Sunday. "Thirty days is out of question. I don't think this problem can be solved within 30 days."
Hotel occupancy in Bangkok has crumbled to 20 percent from about 80 percent in February, squeezing an industry that supports six percent of the economy.
Abhisit said he would soon scale back the government's projection of 4.5 percent annual economic growth this year.
The army has had to deal with a rogue military element that supports the protesters and is allied with former premier Thaksin Shinawatra, who was ousted in 2006 coup and sentenced to prison for corruption after fleeing the country.
The army chief sought to downplay signs of a split in the armed forces, but he acknowledged for the first time some retired and active officers had joined the protest movement.
"Some of those involved in the deadly attacks are still in the military," he said. "But on the division, any big organisation could have that."
Abhisit's six-party coalition government is under intense pressure from upper-class and royalist Thais to rebuff demands from the mostly poor red shirts. He stuck to an earlier offer to dissolve parliament and call elections in December, a year early.
Bangkok, a sprawling city of 15 million people, has been on edge after grenade blasts three days ago killed one person and wounded 88 in the business district, an attack the government blamed on the red-shirts, who deny they were responsible.
MORE ARMY THREATS
The army warned on Saturday it would forcibly disperse thousands of red shirts in a fortified encampment stretching 3 square-km (1.9 miles) in Bangkok's main shopping district, but it wants to first separate militants from women and children.
The army has repeatedly threatened to crack down, saying protesters cannot occupy a key commercial district indefinitely.
Protest leaders are urging supporters to remove their trademark red shirts to make it harder for troops to find them. They threatened other aggressive measures, including laying siege to Central World, the second-largest shopping complex in Southeast Asia, next to the stage at their main protest site.
The shopping centre at the Rajaprasong intersection has been closed since the protesters occupied the area on April 3.
Residents of the capital, weary of the red-shirt tactics, have formed a "multi-coloured" protest group that has drawn thousands to its rallies in the capital.
"This hardening of the battle lines between the two sides does not bode well for Bangkok's security situation and a risk of another, and this time maybe even more violent, crackdown is immediate," risk consultancy IHS Global Insight said in a note.
The government is stepping up accusations the red shirts want to overthrow the monarchy, which the protesters deny, raising the stakes in a country whose 82-year-old king is deeply revered but has appeared rarely in public since entering hospital Sept. 19.
The red shirts say British-born and Oxford-educated Abhisit came to power illegitimately in December 2008, heading a coalition the military cobbled together after courts dissolved a pro-Thaksin party that led the previous government. (Additional reporting by Apornrath Phoonphongphiphat; Editing by Bill Tarrant and Paul Tait)