Jordan's King Abdullah II met his Saudi counterpart in Riyadh Sunday for talks as both nations participate in a US-led bombing campaign against Islamic State group extremists in Syria.

The official Saudi Press Agency said King Abdullah received the Jordanian monarch at his palace.

Since September both kingdoms, along with Bahrain, Qatar, and the United Arab Emirates, have been taking part in American-led air strikes against the IS jihadists in Syria.

Jordan's king warned this month that the fight against IS is a "third world war".

The group has declared a "caliphate" in parts of Syria and Iraq, the nation bordering both Jordan and Saudi Arabia.

IS militants have been accused of widespread atrocities, including beheading Western hostages.

Saudi involvement in the coalition has raised concerns about possible retaliation there, while analysts say Jordan has been placed in danger by joining the international effort.

"During the meeting they discussed overall events at the regional and international level," and how to strengthen bilateral ties, SPA said.

On Thursday Saudi Arabia said it had arrested three alleged IS supporters for shooting and wounding a Danish citizen in Riyadh.

In November, the kingdom blamed IS-linked suspects for killing seven members of the minority Shiite community.

Jordan, which shares a border with Syria as well as Iraq, is grappling with its own home-grown Islamist question.

It also hosts more than 600,000 Syrian refugees.