Xi Jinping is the first Chinese leader to visit Tehran in a decade
Iran and China have pledged closer economic and political ties after talks in Tehran between the two presidents.
China’s Xi Jinping is one of the first world leaders to visit Iran since international sanctions were lifted.
The two leaders signed 17 agreements on a range of issues from energy to boosting trade to $600bn (£420bn).
Iranian President Hassan Rouhani said he and Mr Xi had signed a “comprehensive 25-year document” on strategic relations.
They also discussed terrorism, instability in the Middle East, as well as “science, modern technology, culture, tourism… security and defence issues,” President Rouhani said on Iranian TV.
President Xi is also due to meet Iran’s Supreme Leader Ali Khamenei during his 24-hour visit.
He is the first Chinese president to visit Tehran in over a decade.
International sanctions on Iran were lifted last week after it agreed to roll back the scope of its nuclear activities.
China is Iran’s biggest trading partner and both countries are hoping the strong relationship will continue in Iran’s new post-sanction era, the BBC’s Farhana Dawood reports.