Hong Kong’s university siege stretched into a sixth day on Friday, as medics warned of a humanitarian crisis and the city prepared for weekend elections that will be a key barometer of public support for protesters.

The new police chief, who was sworn in on Tuesday after the Polytechnic University had already been sealed off, is apparently trying to avoid more violent confrontation.

Hong Kong chooses its local councils on Sunday in polls that are normally a sleepy affair with low turnout but are this year expected to serve as a proxy referendum on the protests, which began almost six months ago and have turned increasingly violent in the past couple of weeks.

The commissioner of police, Chris Tang Ping-keung, said there was no deadline to clear the campus, even as he urged protesters inside – estimated to still number about 100 – to come out and surrender.

Some say they are frightened they will be attacked by police while being arrested or after they are detained, pointing to news footage showing officers stamping on the head of a protester from the university, even though he had already been subdued.

With trust in the police at record lows, senior medics warned that the force had crossed another red line this week by arresting dozens of medics and first aiders during the early days of the showdown at the university.

Darren Mann, a surgeon who was in the university with a volunteer first aid team until just before police cut it off on Sunday, said in a letter published in the Lancet medical journal that authorities’ treatment of medics, including the mass detention, violated international norms.

He highlighted a “disturbing” photograph that showed medics lined up in rows on the floor, handcuffed with plastic zip ties, after their arrest for rioting. At a press conference he described the situation in Hong Kong as “a humanitarian crisis for this society”.

On Saturday, the siege will have lasted a week. Despite ebbing numbers, reports of difficult conditions, and the surrender of eight more people overnight, there were still some inside who said they would not give up.

“We have enough [food] for a year,” one protester told a journalist inside the campus. But in a sign that protester ranks may be thinning, she said the university canteen was empty, apart from a volunteer chef, for the first time in a week.

Inside the tight police cordon it is hard to count numbers, because protesters are splintered into small groups. Some roam freely, looking for undercover officers in the area, but others are in hiding, convinced they risk being seized by infiltrators.

Play Video 1:10 Hong Kong protesters escape through sewers in attempt to leave university – video

After dramatic escapes from campus this week, including groups who waded through drains, and others who abseiled off an overpass, some protesters are still looking for ways to get off the campus without surrendering.

Arrest on rioting charges is automatic for those aged over 18, and can carry a jail sentence of up to 10 years. Those who are under 18 have their details taken and are warned they could face charges in future.

“We are feeling a little tired. All of us feel tired but we will not give up trying to get out,” a 23-year-old demonstrator who gave his name only as Shiba told Reuters on Friday. “We spent yesterday trying to find ways to get outside but failed, so we came for some breakfast,” he said.

But an older protester said they had given up on finding a way out, and were focused instead on fashioning new makeshift weapons to defend themselves if police stormed the campus.