Chinese President Xi Jinping hailed Beijing's "solidarity" with Iran on Tuesday as he hosted President Ebrahim Raisi at the start of a three-day trip.
For the first state visit by an Iranian president to China in more than 20 years, Raisi has brought a large trade and finance delegation to Beijing and was earlier greeted by Xi on a red carpet.
"In the face of the current complex changes in the world, times, and history, China and Iran have supported each other (and) worked together in solidarity and cooperation," Xi said, according to state broadcaster CCTV.
Both countries face pressure from Western nations over their positions on Russia's invasion of Ukraine, while Iran is already under strict US sanctions due to its nuclear program.
Iran has emerged as one of Russia's few remaining allies as Moscow has been pushed deeper into international isolation over the invasion.
Western countries have accused Tehran of supplying armed drones to Russia for use in the war in Ukraine, a charge it denies.
In December, Washington outlined what it said was an extensive relationship between Iran and Russia involving equipment such as helicopters, fighter jets and drones.
Moscow's offensive in Ukraine is a sensitive issue for Beijing, which has sought to position itself as neutral while offering diplomatic backing to its strategic ally Russia.
China "supports Iran in safeguarding national sovereignty, independence, territorial integrity and national dignity... and in resisting unilateralism and hegemonism", CCTV reported Xi as saying.
Beijing also "opposes external forces interfering in Iran's internal affairs and undermining Iran's security and stability", and will continue to "promote the early and proper resolution of the Iranian nuclear issue", the Chinese leader said.
"No matter how the international and regional situation changes, China will unswervingly develop friendly cooperation with Iran", Xi added.
According to CCTV, the two sides signed a number of bilateral cooperation documents in the fields of agriculture, trade, tourism, environmental protection, health, disaster relief, culture and sport.
Raisi and Xi met for the first time last September at a Shanghai Cooperation Organization summit in Uzbekistan, where the Iranian president called for expanded ties.
According to Iranian state news agency IRNA, Raisi will take part in meetings with Chinese businessmen and Iranians living in the country.
China is Iran's largest trading partner, IRNA said, citing the 10-month statistics of Iranian customs authorities. Tehran's exports to Beijing stood at $12.6 billion, while it imported $12.7 billion worth of goods from China.
Raisi is being accompanied by the country's foreign minister and the ministers for the economy, roads and transportation, and oil. Also attending is the minister for industry, mining and trade, as well as the minister for agriculture, according to Iranian state television.
His delegation also includes Ali Bagheri, Iran's deputy foreign minister for political affairs and its chief nuclear negotiator.
Chinese foreign ministry spokesman Wang Wenbin said Raisi would meet with Premier Li Keqiang and top Chinese legislator Li Zhanshu.
Raisi's first visit to China comes days after he declared victory over the nationwide protest movement triggered by the death in custody of 22-year-old Mahsa Amini, following her arrest for an alleged breach of Iran's dress code for women.
Authorities say hundreds of people, including dozens of security personnel, have been killed and thousands arrested during the protests, which they generally label as "riots".
The judiciary has sentenced 18 people to death in connection with the protests, according to an AFP tally based on official announcements. Four people have been executed, triggering international outrage.
