Thai protesters besieged several more government ministries Tuesday as part of their efforts to topple Prime Minister Yingluck Shinawatra, defying the imposition of a special security law in the capital.

Demonstrators surrounded the interior, agriculture, transport, and sports and tourism ministries, ordering officials inside to leave, a day after occupying the finance and foreign ministries.

"We have to leave because they (the protesters) will cut the utilities," tourism and sports minister Somsak Pureesrisak told AFP.

Demonstrators gave officials at the interior ministry an ultimatum to leave within one hour, according to an AFP reporter at the scene.

Tens of thousands of demonstrators have rallied against Yingluck and her brother, ousted premier Thaksin Shinawatra, in the biggest street protests since 2010, when more than 90 civilians were killed in a military crackdown.

Yingluck reiterated a vow that authorities would "absolutely not use violence" as she arrived at parliament early Tuesday.

"Everybody must obey the law and not use mob rule to upstage the rule of law," she told reporters.

Police numbers have been increased in Bangkok in response to the expansion late Monday of the Internal Security Act, which gives authorities additional powers to block routes, impose a curfew, ban gatherings and carry out searches.

MPs began debating a no-confidence motion Tuesday, which was put forward by the opposition Democrat Party last week as part of a barrage of legal and institutional challenges to Yingluck's embattled government.

The ruling Puea Thai party holds a comfortable majority in parliament and is expected to win a censure vote.

The recent protests were sparked by Puea Thai plans to introduce an amnesty that could have allowed the return from self-imposed exile of Thaksin, a deeply polarising figure who was deposed by royalist generals in a 2006 coup.

Outrage over that plan failed to ebb after the amnesty was quashed by the Senate on November 11.

There were no immediate signs that authorities were moving to evict the protesters from government buildings although authorities said the demonstrators appeared to be leaving the foreign ministry.