Heavily armed Iraqi peshmerga forces have reached the Turkish border and a first group have entered the town of Kobane as they prepare to join fellow Kurds battling the Islamic State group.

The group of 10 fighters were to co-ordinate with local Kurdish militia who have been holding off an assault by IS jihadists for six weeks, a monitoring group said.

A peshmerga convoy reached the town of Suruc on the Turkish side of the border on Thursday after travelling through southeastern Turkey along roads clogged with flag-waving Kurds, an AFP photographer said.

There it linked up with a second group of peshmerga, but it was unclear when the main force would cross into Kobane.

Officials have said there are about 150 peshmerga fighters in total, armed with machine guns, heavy artillery and rocket launchers.

The IS jihadists were pounding northern areas of Kobane along the border with mortars and heavy artillery on Thursday, a monitoring group said, in an apparent bid to prevent the peshmerga from crossing.

They had also launched an assault on a northern neighbourhood overnight but were pushed back by forces from the Syrian Kurdish People's Protection Units (YPG) militia, the Britain-based Syrian Observatory for Human Rights said.

"The bombardment of the border area will likely delay the entry of the peshmerga" into Kobane, Observatory director Rami Abdel Rahman said.

Kobane has become an important symbol of the battle against IS, an extremist Sunni Muslim group that has seized swathes of Syria and Iraq, committing atrocities and declaring an Islamic "caliphate".

A US-led coalition carrying out air raids against IS has intensified attacks near Kobane in recent days, and the Pentagon said its fighter jets and bombers made 10 strikes in the area on Wednesday and Thursday.