Islamic State forces have entered some eastern neighborhoods of the strategic Kurdish city of Kobani on Tuesday as American planes hit targets around the city in support of Kurdish fighters defending the enclave.

AP reported the ISIS black flag flying over several buildings in the city.

Using armor and artillery, ISIS made significant gains against the lightly armed Kurds, who have been pleading with the world for help in order to prevent a genocide.

BBC:

Fighting between Islamic State (IS) militants and Syrian Kurds is reported to have spread to a southern district of the town of Kobane on the Turkish border, as US-led air strikes continue.

But fighting in the town was less intense than on Monday, when IS took control of three districts in the east.

Witnesses report several loud explosions and plumes of smoke from coalition air strikes.

More than 160,000 Syrians, mainly Kurds, have fled Kobane recently.

If IS captures the town, its jihadists will control a long stretch of the Syrian-Turkish border.

In the latest clashes, the Syrian Observatory for Human Rights (SOHR) activist group said IS had crossed into a southern district of Kobane, taking over many buildings.

However, the group said heavy fighting had forced IS to pull back in eastern districts. It also suggested many IS fighters had been killed in an ambush by Syrian Kurdish fighters.

At least 400 people have been killed in three weeks of fighting for Kobane, according to the SOHR's latest estimate.

The town is now besieged on three sides.

Turkey, who pledged last week to defend Kobani and prevent it from falling into ISIS hands, is so far, on the sidelines. They have massed some troops and armor on the border opposite the besieged city, but are apparently waiting for some guarantees from the coalition before engaging the enemy:

In Turkey, Kurds angered at the government's reluctance to intervene clashed with police overnight in several cities, including Istanbul.

Turkish Kurds and refugees have been involved in confrontations with Turkish security forces on the border for the past two days.

Last week, Turkey pledged to prevent Kobane from falling to the militants and its parliament authorised military operations against militants in Iraq and Syria.

Turkey - a regional superpower with significant troops and armour in the area - seems extremely reluctant to intervene despite a government pledge to do whatever it takes to prevent the Kurdish town of Kobane from falling.

It wants the US-led coalition to agree on a number of things first, including setting up a no-fly zone and a buffer zone in northern Syria and, crucially, a renewed focus on getting rid of President Assad - which remains Turkey's principal objective.

Any "buffer zone" would mean boots on the ground, so that's probably a non starter. And what would President Assad think of the US establishing a no-fly zone over Syrian territory? Turkey views the clash between Islamic State and the US in terms of their war against Assad, not as an end in itself. They also don't want to do anything to help the Kurds unless their engagement helps them more.

Meanwhile, ISIS continues to advance in both Iraq and Syria. We are losing this war because IS is all in and we're not. Can't get any simpler than that.