Tunisian police used teargas on Monday to try to disperse protesters who gathered at the prime minister's office as part of a campaign to remove a government linked to the ousted president, Zine al-Abidine Ben Ali. Reuters witnesses saw the protesters, most of whom came to the capital from marginalised rural areas, surge into the compound area by the office and break several windows in the finance ministry building. More than a week after the prime minister, Mohamed Ghannouchi, took the reins of an interim coalition following the overthrow of Ben Ali, he and other former loyalists of the feared ruling party face mounting pressure to step down. But the shape any eventual popular leadership might take is unclear. Formal opposition parties exist, but are not well known after decades of oppression. A hitherto banned Islamist party has called for early elections and may find support. The foreign minister, Kamel Morjane – who served under Ben Ali – said he would not step down for the moment. "As for my post as a minister, I see it as a way to help my country at a difficult moment. I am not insisting on staying in the government," he told France's Le Figaro newspaper. He said his main concern was that the country might "descend into chaos". For days, protesters have gathered at the premier's office, limited in numbers but tolerated by police anxious for their own futures after Ben Ali's departure. The demonstrators enjoy wide support among a population unused to free political expression. Since Ben Ali fled to Saudi Arabia earlier this month, police had only used teargas once against protesters, who had gathered on the central Habib Bourguiba Boulevard. On Sunday, amid weekend calm, hundreds of people who had been driven to the capital in a "freedom caravan" surrounded Ghannouchi's building in central Tunis. Many were from Sidi Bouzid, a bleak city in central Tunisia where the Jasmine revolution over poverty, corruption and political repression was sparked a month ago by the suicide of a young man.