BEIJING, Sep 17 (AFP) - China's top diplomat Wang Yi will visit Russia from September 18-21 for security talks, his foreign ministry said Monday, the latest in a series of high-level visits and phone calls between the two sides.

China and Russia are strategic allies, with both countries frequently touting their "no limits" partnership and economic and military cooperation.

Their ties became even closer after Russia invaded in Ukraine in February last year, which China has refused to criticise.

China's foreign ministry said in a statement that Wang "will go to Russia to hold the 18th round of the China-Russian Strategic Security Consultations (SSCC) from 18 to 21 September" at the invitation of Nikolai Patrushev, secretary of Moscow's security council.

Last month Defence Minister Li Shangfu visited Russia and Belarus, and called for closer military cooperation.

In recent months the two countries have carried out joint sea and air patrols, the latter of which caused South Korea to deploy fighter jets as a precaution.

The high-level contact looks set to ramp up, with an aide to Vladimir Putin saying in July that the Russian president was planning to visit China in October.

In March President Xi Jinping made a state visit to Moscow and declared relations between the two countries were entering a new era.

China has sought to position itself as a neutral party on the Ukraine war, while offering Moscow a vital diplomatic and financial lifeline as its international isolation deepens.