BANGKOK (AFP) - Thai political protests spread outside the capital on Wednesday as opposition demonstrators predicted a victory within days in their bid to overthrow Prime Minister Yingluck Shinawatra's crisis-hit government.

Protest leader Suthep Thaugsuban urged protesters to march on Wednesday on a large office complex on the northern outskirts of Bangkok that houses a number of government agencies, as the protests spread to several other provinces. "We are very upbeat and I think we will win in a few days," Mr Suthep, a former deputy premier and key opposition figure, told reporters as he left his de facto headquarters at the occupied Finance Ministry.

He on Tuesday called for the creation of an unelected administration to run the country, in the clearest indication yet that the demonstrators are seeking to suspend the democratic system. "If we demolish the Thaksin regime ... we will set up a people's council which will come from people from every sector," he said. "Then we will let the people's council pick good people to be the prime minister and ministers."

Demonstrators have also besieged several government offices in the opposition's southern stronghold, including on the island of Phuket, a top destination for foreign tourists, where several hundred protesters massed on Wednesday outside a provincial hall.

Raucous, whistle-blowing crowds have besieged government buildings to challenge Ms Yingluck and her brother, ousted premier Thaksin Shinawatra, in the biggest protests since mass street rallies in 2010 that turned deadly.

While the demos have so far been largely peaceful, the fear is that they could descend into another bout of street violence in a country that has seen several episodes of political unrest since Thaksin was ousted in a 2006 coup.

Ms Yingluck's "red shirt" supporters, who have held their own rally at a sports stadium in the capital, appeared to be losing patience with the growing protests although they have refrained from taking to the streets in the latest standoff.

"The current situation is near breaking point," said red-shirt leader Jatuporn Prompan, calling for more supporters to join their gathering.

But "we will only move out (on to the streets) if there's a coup", he added.