Hungary's Defence Minister Csaba Hende resigned after a national security council meeting was held to discuss the huge influx of refugees and migrants arriving in the country.

Prime Minister Viktor Orban, a right-winger who has pushed for a hard line on Europe's immigration crisis, accepted Hende's resignation on Monday and offered the job to Istvan Simicsko, also a member of his Fidesz party.

Syrian refugees embark on journey from Hungary to Austria

The country, which has seen more than 100,000 people arrive -many fleeing conflict in the Middle East, last week proposed measures that would allow it to deploy the army to its borders in a bid to stem the inflow.

Greek island 'on the verge of explosion'

The Greek island of Lesbos is "on the verge of explosion" with the arrival of more than 15,000 mainly Syrian refugees, pushing local resources to the limit, the immigration minister said.

Yiannis Mouzalas told To Vima radio on Monday that boats taking refugees to the Greek mainland would soon be using a second port to ease pressure on the island of 85,000 inhabitants.

"Mytilene currently has 15,000-17,000 refugees and this is the official figure from all services," Mouzalas, a junior interior minister, told the station.

"We are placing emphasis here because the situation is on the verge of explosion," he said.

Syrian refugees disembark on the island of Lesbos [Getty Images]

Second departure point

The minister said the second departure point would open at the fishing village of Sigri in coming days.

Lesbos is one of several Greek islands struggling with an influx of thousands of refugees, many of them Syrian refugees, setting sail from the nearby Turkish coast.

"We hope that in the next five days the [islanders] and the refugees will see clear signs of improvement," he said.

More than 230,000 people have landed on Greek shores this year, with the numbers soaring in recent weeks as people seek to take advantage of the calm summer weather.

More than 230,000 people have landed on Greek shores this year  [AP]

UK promise

Meanwhile on Monday, British Prime Minister David Cameron said the UK will resettle up to 20,000 Syrian refugees from camps in Turkey, Jordan and Syria over the next five years.

The figure represents a vast expansion of Britain's refugee programme, a change signaled by Cameron last week.

He told Parliament that Britain has a moral responsibility to act, citing shocking images in recent days.

Cameron said vulnerable children and orphans will be given priority. New arrivals will be given five-year "humanitarian protection" visas upon arrival in Britain.

Source: Agencies