SEOUL, South Korea — The United States and South Korea began naval exercises on Sunday that were meant as a warning to North Korea for recent provocations, including last week’s deadly artillery attack on a island populated by South Koreans in the Yellow Sea.

At the same time, China stepped up its diplomatic efforts to cool tempers in the region, with a senior envoy holding a meeting on Sunday morning with South Korea’s president and Beijing announcing that it had invited a senior North Korean official for talks this week. China also called for an emergency meeting of the so-called six-party talks on North Korea's nuclear program, news agencies reported.

North Korean artillery was heard Sunday on the island, though no shells landed there and South Korea considered it just a drill, according to a spokesman for South Korea’s Joint Chiefs of Staff. The North Koreans also shot off artillery on Friday, after a visit by an American general to the island, called Yeonpyeong.