Red shirt military advisor wounded in Bangkok

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 today.

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' 1.2 square mile fortified encampment to close tomorrow.

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 mostly rural and urban poor protesters refused to leave as their leaders challenged the government from behind medieval-like walls made from tyres and wooden staves soaked in kerosene and topped by razor wire.

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 tomorrow. Several stations in an elevated train system were shutting early. Public transportation was being diverted from the area.

The mood at the protest site turned quickly in the afternoon from festive to tense. Leaders took turns on the stage to call for more protesters to come to the encampment, chanting "come out, come out" and threatening to lay siege to Prime Minister Abhisit Vejjajiva's house and an infantry barracks where he has taken refuge if there is a crackdown.

Abhisit is under enormous pressure to end the two-month crisis that has killed 29 people, wounded more than 1,000, paralysed parts of Bangkok and slowed growth in Southeast Asia's second-biggest economy.

But analysts and an army source close to Army Chief Anupong Paochinda said an immediate crackdown is unlikely despite the threats.

"It's hard to say if or when the crackdown will be because we have to evaluate by the hour. We don't want casualties so we have to keep the pressure up so people are too tired to resist.

"Casualties will be bad for us as well."

Analysts said potentially high casualties have prevented the army from going in.