US air strikes have destroyed four Islamic State (Isis) tanks in the eastern Syrian province of Deir el-Zour, US central command has said.

It said 10 air strikes were carried out in Iraq and Syria targeting the extremist group on Thursday and Friday.

US central command’s announcement came hours after a UK-based monitoring group, the Syrian Observatory for Human Rights, said Isis bases and oilfields had been hit in overnight sorties.

The US military said that in Iraq it wiped out three Isis Humvees as well as another vehicle with five air strikes in Kirkuk, in the north, while an air strike west of Baghdad destroyed a guard shack, armed vehicle and bunker. Another air strike destroyed four armed vehicles, an Isis command and control node and a checkpoint in Qaim, in north-west Iraq, near the Syrian border. There were three strikes in Deir al-Zour, eastern Syria, where US-led forces started bombing Isis militants on Tuesday.

The US has been bombing bases of the al-Qaida splinter group in Iraq since last month.

Also on Friday, Turkey raised the prospect of joining the international coalition amid growing pressure from its western allies. Ankara has frustrated the west with its failure to commit to concrete action and to stop foreign jihadis entering Syria through its border.

Isis militants are just a few kilometres south of the Turkish border, having advanced on the mainly Kurdish Syrian town of Ain al-Arab, also known as Kobani. Turkey’s caution had been attributed, partly at least, to the fact that dozens of its citizens were being held hostage by Isis in Iraq but they were freed last weekend.

The Turkish prime minister, Ahmet Davutoglu, told a meeting of his ruling party in Ankara: “If any military operation or a solution carries the perspective of bringing peace and stability to the region, we will support it. We will take whatever measures our national security requires.” He did not give any details about what such measures could entail.

Meanwhile, Denmark announced that it was sending seven F-16 fighter jets to take part in air strikes against Isis in Iraq. The deployment, which will last for 12 months, includes 250 pilots and support staff. Britain and Belgium were debating their involvement in the coalition on Friday.

The Friday morning air strikes hit Isis bases and positions on the outskirts of the city of Mayadinm, the Observatory said.

Deir el-Zour, which borders Iraq, is almost entirely controlled by Isis militants and was a major oil-producing province before the Syrian conflict began more than three years ago.

Oil has been a top source of revenue for Isis militants, and air raids on Thursday targeted refineries controlled by the group. The strikes also seem to be intended to hamper Isis’s ability to operate across the border in Iraq, where it also controls territory.

The Observatory said there were casualties from the earlier strikes but did not give details.