The chief military advisor of Thailand's anti-government protesters was injured in the head, after an explosion and bursts of automatic gunfire were heard near Bangkok's business district on Thursday night.
Khattiya Sawasdipol, a suspended army specialist in charge of security at an encampment occupied by thousands of "red shirt" demonstrators, was admitted to an intensive care ward after being shot, said the state Narenthorn Emergency Medical Service.
It had no other details.
Khattiya, better known as "Seh Daeng" (Commander Red) enjoys a cult following among some red shirts and soldiers, but has been dubbed a "terrorist" by Thailand's government, which accuses him of involvement in dozens of grenade attacks that have injured more than 100 people.
The army had earlier said it was planning a huge lockdown around the fortified encampment of the red shirts, who have defied warnings to end their five-week occupation of an upmarket Bangkok shopping district.
The Thai military said it would deploy armoured vehicles and shut roads surrounding thousands of defiant protesters on Thursday, forcing businesses to evacuate workers as tensions rise in the deadliest political crisis in two decades.
The army said its armoured vehicles will bolster checkpoints, stopping protesters from entering the area, and urged businesses on roads leading into the protesters' 3 sq-km (1.2 sq-mile) fortified encampment to close on Friday.
Army spokesman Sansern Kaewkamnerd said authorities tasked with resolving the crisis will also seek cabinet approval to invoke a state of emergency in 15 northern and northeastern provinces, which are stronghold of protesters to prevent any mobilisation.
The government estimated the crowd size at 10,000 but Reuters witnessses put it at more than 20,000.
"We will send out groups to surround these vehicles to prevent them from advancing," Jatuporn Prompan, a protest leader, told supporters. "We believe the army will try to crack down this evening or tomorrow morning."
Companies and embassies across the area told employees to leave work early and activated back-up plans for Friday. Several stations in an elevated train system were shutting early. Public transportation was being diverted from the area.
The prime minister on Wednesday cancelled a proposed Nov. 14 election under his "national reconciliation" plan and called off talks with the protesters, raising speculation of a crackdown.
Foreign investors have turned negative since violence flared in April and have sold $584 million in Thai shares in the past six sessions, cutting their net buying so far this year to $607.6 million as of Wednesday.
"The markets have no idea what to make of the situation. It seems like we're heading back to square one," said Sukit Udomsirikul, a senior analyst at brokerage Siam City Securities.
Disparate views among protest leaders -- from radical former communists to academics and aspiring lawmakers -- make it difficult to reach consensus. Many face criminal charges for defying an emergency decree and some face terrorism charges carrying a maximum penalty of death.
Several harbour political ambitions and need to appease rank-and-file supporters. Others fear ending the protest now would be a one-way ticket to jail. Some hardliners advocate stepping up the protests to win the fight once and for all.
The red-shirted protesters, have said they would only disperse if a deputy prime minister faces criminal charges over a deadly April clash between troops and protesters.
Red shirt military advisor wounded in Thai capital
The chief military advisor of Thailand's anti-government protesters was injured in the head, after an explosion and bursts of automatic gunfire were heard near Bangkok's business district.