The United Nations' envoy to Syria, Staffan de Mistura, said the international community must act to defend the border town of Kobani from "Islamic State" (IS) fighters.

Eastern and southwestern parts of the town were already believed to be controlled by the militant group by Wednesday morning. IS has surrounded the area on all sides but the Turkish border to the north. From the Turkish side, two militant flags have been seen flying over the eastern side of Kobani.

"The world, all of us, will regret deeply if (IS) is able to take over a city which has defended itself with courage but is close to not being able to do so. We need to act now," de Mistura said on Tuesday.

"The international community needs to defend them. The international community cannot sustain another city falling under (IS)."

British-based monitoring group The Syrian Observatory for Human Rights said Kurdish fighters had some success in repelling the jihadists in parts of the town. However, there was a call from the town's local leadership for more to be done.

"The airstrikes should be intensified," said Idriss Nassan, deputy foreign minister of the self-proclaimed Kobani autonomous canton.

"There should be strikes at night and during the day and weapons should be given to People's Protection Units (Kurdish militia) that could be considered part of the international coalition to fight terrorism."

At least 200,000 civilians have fled the town and its surroundings, with many crossing into Turkey.

Turkish troops stationary

Turkey warned earlier on Tuesday that militants were said to be on the verge of taking over Kobani, prompting the UN envoy to make his appeal.

Turkey has stationed tanks and ground forces along the border near Kobani, also known as Ayn Arab. However, despite the Turkish government saying it would not let the town fall, there has so far been no intervention and some are skeptical that Ankara is willing to act.

The US, which has been launching airstrikes aimed at stopping the militants' advance on Kobani, said it was "very concerned" for Kurdish civilians still inside the town.

IS has been accused of carrying out widespread atrocities in the areas of Iraq and Syria that it has taken over, including mass executions, abductions, torture and forcing women into slavery. Ethnic and religious minorities have been targeted in particular.

rc/jm (AP, AFP, dpa, Reuters)