The number of refugees fleeing the bloodshed in Syria could reach 700,000 by the end of the year, the United Nations has warned.

About 294,000 refugees have already crossed into the neighbouring countries of Jordan, Iraq, Lebanon and Turkey since the conflict began 18 months ago.

The UN refugee agency said more money was urgently needed to care for the hundreds of thousands expected to arrive in refugee camps over the next three months.

“We are running out of time,” Panos Moumtzsis, the UN chief co-ordinator for Syrian refugees, told reporters in Geneva.

He said humanitarian agencies need £305m ($487.9m) to sustain their operations until the end of the year. At present, only £88m is available – just 29% of the total needed.

With winter approaching, he said money was urgently needed for tents, clothing, blankets and heaters.

Riots erupted this week at the UN-run Zaatari refugee camp in northern Jordan after Syrians complained about poor living conditions at the 30,000-strong compound.

Police used tear gas to quell the violence and eight Syrians were charged with “unlawful assembly and carrying out riots”.

More than 20 officers were injured in similar disturbances at the camp last month.

Jordan, which is hosting more than 200,000 Syrian refugees, has complained of limited resources to cope with the growing number of Syrians flooding into the country.