China plans to increase its defense spending by 7.2 percent this year, according to a budget plan unveiled at the opening session of the country's parliament.

The National People's Congress began on Tuesday. The government's budget plan includes defense spending of 1.665 trillion yuan, or about 230 billion dollars.

China is stepping up its activities in the East and South China seas, and its military is thought to possess more naval vessels than the United States.

The US Defense Department said in a report last year that China is estimated to have more than 500 operational nuclear warheads. It said the nuclear arms buildup is happening faster than projected.

China is also promoting the use of military and civil resources to drive innovation under its so-called "military-civil fusion" strategy, with a focus on artificial intelligence.

A spokesperson for the National People's Congress told reporters on Monday that China's military spending in proportion to GDP is lower than that of the United States and other major military powers.

But critics say China's national defense budget does not accurately reflect real spending, as it is believed to exclude the costs of foreign purchases of military equipment and R&D.

The planned 7.2 percent growth in spending is about the same as last year. Observers say this shows China's resolve to enhance its military strength, despite the uncertainties over the country's economy.