More than a thousand Hong Kong tour group visitors in Bangkok were safe and were trying to steer clear of protest hotspots, the Travel Industry Council said.

"Residents intending to visit the country or are already there should monitor the situation, exercise caution, attend to personal safety and avoid protests and large gatherings of people," the Security Bureau website said.

The United States, Britain, France, Japan, China, Taiwan, South Korea and Singapore are among the 23 countries which have issued travel advisories, according to the .

The turmoil comes as Yingluck's government faces a no-confidence motion in parliament introduced by the opposition Democrats, who have not won an elected majority for two decades.

Video: Crowds besiege a government building in Bangkok

While the protests have so far been largely peaceful, there are fears 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.

Up to 10,000 protesters gathered yesterday at a large office complex on Bangkok's northern outskirts that houses several key government agencies.

Their numbers swelled dramatically as defiant protest leader Suthep Thaugsuban marched into the compound, flanked by thousands of other demonstrators.

"We are very upbeat and I think we will win in a few days," the former deputy premier said earlier as he left his de facto headquarters at the occupied finance ministry.

Suthep 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."

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

"The situation is serious, but it is under control," Pracha Promnog, a deputy prime minister, said after a meeting with Yingluck. But he warned that protesters would not be allowed to occupy Government House or parliament.

A court has issued an arrest warrant for Suthep for his role in the ministry seizures and authorities have urged the veteran politician to surrender.

The recent protests were sparked by plans by the ruling Puea Thai party to introduce an amnesty that could have allowed Thaksin's return from self-imposed exile.

The Senate blocked the controversial bill, but demonstrators have since broadened their goal and now want to topple the government.