Saudi Arabia's Crown Prince Mohammed bin Salman on Tuesday spoke of the kingdom's concerns about Iran's nuclear programme as Gulf leaders gathered in Riyadh for the GCC summit.

Speaking after leaders from Bahrain, Kuwait, Oman, Saudi Arabia, the UAE and Qatar gathered in the Saudi capital, Prince Mohammed said the kingdom “stresses the importance of seriously and urgently dealing with Iran's nuclear and ballistic missile programme to ensure regional and international security and stability".

The GCC states come together every year to discuss trade, politics and security issues. Iran was expected to be high on the agenda this year amid international efforts to revive a nuclear pact with Tehran.

Prince Mohammed said his country would continue to make efforts to achieve stability in the region. He said “the kingdom also watches with concern the unfolding developments in Afghanistan and urges international and regional efforts to offer assistance to the country".

GCC Secretary General Nayef Falah Mubarak Al Hajraf said that an act of aggression against any one of the Gulf states was considered an act against all of the bloc's member states.

The Secretary General called for unity against threats amid an escalation in missile and drone attacks against the kingdom carried out by Yemen's Houthi rebels. He said the Gulf states would hold joint military training exercises in Saudi Arabia's Eastern Region next month.

Mr Al Hajraf also said that the Gulf leaders agreed on setting up plans that aim to reach environmental sustainability goals, fight global change and achieve Saudi Arabia's vision of a “circular carbon economy” which it announced as host of the G20 summit last year.

Praise for Prince Mohammed's Gulf tour

Speaking at the summit, Bahrain's King Hamad bin Issa and Crown Prince Salman bin Hamad hailed the Saudi Crown Prince's recent tour of the Gulf, which sought to enhance co-ordination between GCC states and strengthen the work of the regional body.

“We laud the results of the Gulf visit by Saudi Crown Prince Mohammed bin Salman which has positively paved the way for this summit,” said King Hamad.

He also commended the Crown Prince's aim to “bring different points of views closer and overcome challenges” during his trip, which included Bahrain, Oman, the UAE, Qatar and Kuwait.

Leaders from across the Gulf began arriving in Saudi Arabia on Tuesday evening, with Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, leading the UAE's delegation. He was welcomed to the summit by Prince Mohammed.

Shortly before he arrived in Riyadh, Sheikh Mohammed said: “We need a strong start for the fifth decade of the Gulf Co-operation Council. We are looking forward to economic integration. We are looking for real and deep co-operation.”

Oman's Deputy Prime Minister, Sayyid Fahad bin Mahmoud Al Said, was the first to arrive in Saudi Arabia with his country's delegation and he held talks with Prince Mohammed.

The country's Foreign Ministry shared pictures of the Omani delegation departing for Riyadh.

'Signs of positive political harmony are on the horizon'

The summit is the first time Gulf leaders met since signing the historic AlUla agreement in January to end a rift with Qatar that lasted three-and-a-half years.

Saudi Arabia, Bahrain, the UAE and Egypt had cut diplomatic, trade and transport ties with Qatar in 2017 over its support for extremist groups.

Qatar's Emir, Sheikh Tamim Al Thani, was warmly greeted by Prince Mohammed as he landed at the airport late on Tuesday. The two officials could been seen smiling broadly and embracing.

Sheikh Tamim's presence at the summit is seen as a sign of improving relations between Doha and the GCC states.

In the run-up to the summit, Qatar's former prime minister Sheikh Hamad bin Jassim Al Thani said “signs of positive political harmony are beginning to appear on the horizon” in the Gulf region.

Sheikh Hamad said he expected the summit to rehabilitate the GCC “and prepare it for a new steady start in various fields, which will be studied and realistic”.

Shortly after the Qatari delegation's arrival at the airport, Bahrain's King Hamad bin Issa was greeted by Prince Mohammed, with the Saudi royal kissing the king's forehead.