The leaders of North Korea and China have marked the 75th anniversary of their diplomatic relations by exchanging messages that expressed hopes for stronger ties, as outsiders raised questions about their relationship.

Leaders of China and North Korea on Sunday traded a vow of enhanced bilateral cooperation on the 75th anniversary of the establishment of diplomatic relations between the two countries, state news agency KCNA reported.

The alliance between China and North Korea — and more broadly, Iran and Russia — is a growing security concern for the West.

Sunday marked the 75th anniversary of the establishment of diplomatic relations between North Korea and China, but both members of this “blood alliance” are refraining from pomp and circumstance. While some assert that relations between the two countries are shaky,

The leaders of North Korea and China marked the 75th anniversary of their diplomatic relations on Sunday by exchanging messages that expressed hopes for stronger ties, as outsiders raised questions about their relationship.