King Salman meets Turkish President Erdogan.

Turkish President Recep Tayyip Erdogan arrived for talks in Saudi Arabia on Monday and met with King Salman to further strengthen ties as part of a Gulf tour.

The two Sunni powers have become increasingly close over the past year, sharing in particular a backing for the opposition in Syria’s war.

Before beginning his Gulf trip in Bahrain on Sunday, Erdogan said Turkish troops and their Syrian rebel allies had entered the center of Al-Bab, ISIS’ last stronghold in the northern Syrian province of Aleppo.

In Bahrain, Saudi Arabia’s island neighbor and close ally, Erdogan met King Hamad and other officials.

In April last year Salman visited Erdogan, who awarded him a rare honour, the Order of State. Turkey then began hosting Saudi warplanes at its Incirlik air base as part of the US-led coalition against ISIS jihadists, who are among an array of factions fighting in Syria.

Ankara has taken on an increasingly important role with Moscow and Iran as a powerbroker in the Syria conflict.

In January Turkey, along with Assad allies Russia and Iran, sponsored talks in Kazakhstan between Syrian rebels and government officials.

There was no breakthrough, but Kazakhstan has proposed another round in Astana this Wednesday and Thursday, before United Nations-sponsored peace talks resume in Geneva on February 23.

On Monday in Manama, Erdogan called for a “safe zone” in northern Syria where people displaced by the war could go.

The positions of Saudi Arabia and Turkey are “absolutely identical” on Syria, Saudi Foreign Minister Adel al-Jubeir said last week in Ankara.

He attended the first meeting of a coordination council to enhance ties between the two countries.

Both Riyadh and Ankara are hoping for better relations with Washington under President Donald Trump.

For Turkey, ties were strained under Barack Obama because of Washington’s support for Syrian Kurdish militia, which Ankara views as “terrorist” groups.

Saudi Arabia felt Obama was reluctant to get involved in the civil war in Syria and was tilting towards its Shiite-dominated regional rival Iran.

From Riyadh, Erdogan on Tuesday will journey to Qatar, with which Turkey has maintained strong ties for years. Qatar also hosts a Turkish military base.