Usage of commas

On Wednesday, China's foreign ministry said it had lodged a diplomatic complaint with London, denouncing Hunt as "shameless" for his warning of consequences if Beijing breached the Sino-British declaration.

Is ',denouncing' a short version of ',and he or she(=China's foreign ministry ) denounced...' or ,'and it(=a diplomatic complaint) denounced...'

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Last month, the U.S. and 23 other countries sent a letter to the UN Security Council's North Korea sanctions committee, calling for "urgent actions" to deal with the North importing far more refined petroleum than the annual cap of 500-thousand barrels.

Is ',calling for' a short version of ',and they(=the U.S. and 23 other countries ) called for' or 'and it(=a letter called for...'

I am always and still confused with usage of commas and it will be the most challenging for me.

What do you native English speakers think? Thank you so much as usual in advance.