In the far northwestern corner of Bosnia, as the bitter autumn cold sets in, hundreds of migrants including from Pakistan are stuck in a forest as they try repeatedly to get into Croatia... and often fail.

The poor country is a passageway for countless migrants trekking the "Balkans Route" towards their Western European dream but for many, that throughway has become a dead end.

Dozens try every day to get into Croatia illegally, climbing a wooded mountain that borders both countries, some using GPS coordinates sent by those who succeeded.

But the police await and most are pushed back into Bosnia, where authorities are closing shelters under pressure from exasperated locals.

In a forest close to the small town of Velika Kladusa just three kilometres from the border with Croatia, Mahbubur Rahman is preparing for his fourth crossing attempt.

The 23-year-old left Bangladesh in February 2019 and is determined to reach Italy before the winter.

He's been living in a makeshift camp for a month with 300 other Bangladeshis, mostly young men, sleeping under plastic tarpaulin that no longer protects him from the cold at night.

Temperatures will soon drop below zero degrees Celsius.

"It's really cold now, it's raining. We don't have food, water, and people are falling ill," he tells AFP.

- 'Torture' -

In daytime, some wash in a nearby stream. Others bring back water to make a meagre meal out of rice or pasta.

Mahbubur Rahman says the constant pushbacks by Croatian police are "torture".

"They take everything, our jackets, bags, food, shoes, money."

The migrants, often from Afghanistan, Pakistan, Bangladesh or Morocco, also accuse Croatian police of beating them up. In Zagreb, that's strenuously denied.

Then there are frequent fights between migrants of different nationalities.

On Wednesday, two Pakistanis were killed and around 20 injured in a brawl with a group thought to be from Afghanistan, police said.

The International Organization for Migration (IOM) estimates that around 2,500 migrants are homeless in Bosnia, a figure it believes will shoot up as authorities close some shelters.

"We're fast heading towards a humanitarian crisis," warns Peter Van der Auweraert, the IOM's Bosnia Representative.

"We risk finding ourselves in a situation where there will be 4,000 to 4,500 homeless people by the end of November... in this region where there is a lot of snow and where it's cold," he tells AFP.

- The 'inhumanity of it all' -

On Wednesday, authorities closed a site managed by the IOM in Bihac in northwestern Bosnia that had housed up to 2,000 migrants.

For a month beforehand, no-one new had been able enter and those who left to attempt a new "game", as migrants call their border-crossing attempts, were banned from coming back if they failed.

"Beyond the inhumanity of it all, difficult to see how today's action addresses legitimate concerns of local citizens. It will only add to number of people already sleeping outside in and around #Bihac," Van der Auweraert said on Twitter.

Regional leader Mustafa Ruznic retorted that the camp was a "hotbed of security and sanitary problems".

Local authorities also want to rapidly close a reception centre in Velika Kladusa which houses 700 people and is also currently banning any new migrant from entering.

Residents in both towns have protested several times, demanding the closure of the camps, and the issue is politically sensitive as municipal elections approach in November.

In a statement, the EU delegation in Bosnia said "these irresponsible actions put lives at risk".

Kafil Kashr, a 48-year-old journalist who fled Indian-administered Kashmir, has tried and failed to cross into Croatia 14 times in a year-and-a-half. He's currently resting before a new "game".

"We came here to seek salvation. But we are kicked, we are beaten. They might as well kill us next time. We're fed up," he says.