HONG KONG (AFP) - Tensions rose in Hong Kong after police were seen unloading boxes of rubber bullets and other equipment to disperse crowds outside government buildings.

Police had earlier carried long wooden boxes and metal barrels into the legislative headquarters, as angry protesters tried to block their path.

Pictures shared widely on social media and television showed one barrel with the words "Round, 38mm rubber baton multi" written on it.

Another barrel had the words "1.5 in, CS" emblazoned on it, a possible reference to CS gas, a form of tear gas.

The city authorities said on Thursday they wanted the streets cleared around the government headquarters with more than 3,000 civil servants expected to return to the headquarters after a two-day public holiday.

"The government and the police appeal to those who are gathering outside the police headquarters, CGO (central government offices) and CEO (Chief Executive's office) not to block the access there and to disperse peacefully as soon as possible," the government said in a statement.

Protesters have been occupying several streets and intersections in the city for five days in a push for free elections of the city's leader and are calling for current Chief Executive Leung Chun-ying to step down.

"If protesters surround government property... causing total blockage, seriously affecting public safety and public order... the police will not allow this violent act to happen," police spokesman Hui Chun-tak said.

The late afternoon resupply by police officers caused widespread alarm among protesters as their leaders issuing fresh calls for people to swell their ranks.

Andrew Shum, a member of protest group Occupy Central, said: "I'm worried that the police will use force to disperse the movement tonight. Everyone is discussing what they are going to do next."