BANGKOK: Thai opposition protesters marched on key state communications targets Saturday after vowing a final push to topple the government, as the capital braces for mass rival rallies.

Defiant demonstrators have besieged key government buildings in Bangkok in the biggest street protests since mass rallies in 2010 degenerated into the kingdom's worst civil strife in decades.

The protesters — a mix of royalists, southerners and the urban middle class sometimes numbering in their tens of thousands — are united by their loathing of former premier Thaksin Shinawatra.

The controversial former telecoms tycoon was ousted in a military coup in 2006 and lives in self-imposed exile, but he is widely believed to be the real power behind the embattled government of his younger sister Yingluck Shinawatra.

Several thousand anti-government protesters were scattered across five bases in the capital Saturday, according to city police.

But turnout is expected to spike over the weekend as organisers seek a final push ahead of celebrations for revered King Bhumibol Adulyadej's birthday on December 5, which is traditionally marked in an atmosphere of calm and respect.

They have declared Sunday a “day of victory”, with plans to gather near the heavily guarded Government House, besiege more important buildings — even Bangkok's zoo — and to tighten their blockade of government ministries.

Protesters on Saturday began surrounding offices of Telephone Organisation of Thailand (TOT) and Communications Authority of Thailand (CAT), two key state telecoms firms.

“We will control the area, like we did at the finance ministry, and ask staff not to work. So on Monday everything will shut down,” rally spokesman Akanat Promphan told AFP.

But the ICT ministry insisted that back-up systems were in place and communications in Thailand would not be affected.

Protesters are demanding the end of the “Thaksin regime” and want to replace the government with an unelected “people's council”.

Provocative protests

Demonstrators on Friday forced open the gates of the compound of the army headquarters in Bangkok and occupied the lawn inside for several hours, calling on the military to support their fight to bring down the government.

It was the latest in a string of provocative moves targeting a symbol of state power, which have made headlines but failed to rattle the government into acting to disperse their rallies.

“The prime minister has given clear orders for authorities to deal leniently with protesters and not to use violence,” a deputy prime minister Pracha Promnog said on television Saturday.

Yingluck has faced down a barrage of legal and institutional challenges in recent weeks from the opposition Democrat Party, many of whose members have taken to the streets with the anti-government protesters.

Her ruling Puea Thai party came to power in 2011 elections on a wave of Thaksin support, after a bloody 2010 military crackdown on “Red Shirt” protests under the then Democrat-led government left some 90 people dead.

The pro-Thaksin Red Shirts also plan a weekend rally, with around 20,000 people gathered in a stadium in Bangkok early Saturday.

But they have so far shown no intention of taking to the streets of the capital.

Thaksin is adored by many of the country's rural and urban working class but hated by many southerners, middle-class Thais and the Bangkok elite, who see him as corrupt and a threat to the monarchy.

He remains a hugely divisive figure seven years after he was deposed by royalist generals.

Pro-Thaksin parties have won every election for more than a decade but Yingluck has given no indication that she is thinking of calling fresh polls as a way out of the crisis.

In a statement released Friday, army chief Prayuth Chan-O-Cha urged protesters to respect “the democratic process under the law”, urging people to come together ahead of the king's birthday.

The generals are traditionally seen as staunch defenders of the monarchy with close links to its supporters in the royalist “Yellow Shirt” protest movement — the arch-rivals of the Red Shirts.

But they have so far shown little appetite for getting involved in the latest standoff.

The protests snowballed after the ruling party tried to introduce an amnesty that could have allowed Thaksin's return, and have continued despite the Senate's rejection of the bill.