Thailand's deputy prime minister on Sunday rejected an ultimatum by thousands of protesters demanding the government step down, raising the prospect of more rallies in the turmoil-wracked kingdom.

Suthep Thaugsuban, one of three deputy prime ministers, said supporters of ousted premier Thaksin Shinawatra were free to repeat Saturday's mass rally, but insisted the new Democrat Party-led government would stay in office.

"This is not the time for the dissolution of parliament --people want the government

to go ahead with administering the country," he told reporters.

About 30,000 Thaksin sympathisers clad in their signature red shirts and waving banners reading "Bring Back Democracy" marched to the prime minister's Government House offices in Bangkok late Saturday before dispersing.

Their main targets are figures in the six-week-old government who are linked to the People’s Alliance for Democracy (PAD), a royalist group whose protest campaign last year helped topple the previous Thaksin-linked ruling party.