Russian President Vladimir Putin and North Korean leader Kim Jong Un signed a new partnership that includes a vow of mutual aid if either country is attacked, during a Wednesday summit that came as both face escalating standoffs with the West.

The deal, which the leaders said covered areas including security, trade, investment, and cultural and humanitarian ties, could mark the strongest connection between Moscow and Pyongyang since the Soviet Union collapsed in 1991. Both leaders described it as a major upgrade of their ties.