Japan's ambassador has called on the Chinese government to take stronger measures to protect its citizens as thousands of protesters demand a boycott of Japanese products and shout anti-Japanese slogans.

The protests are aimed at Japan's bid to become a permanent U.N. Security Council member and have been made more emotional by Chinese objections to how Japanese school textbooks recount Japan's 20th century military campaigns.

Sunday's protest by about 20,000 protesters in two cities in the southern Guangdong province followed Saturday's angry demonstration at Japan's embassy in Beijing.

About 10,000 Chinese surrounded Japan's consulate in Guangzhou, capital of the Guangdong province, carrying anti-Japanese banners and Chinese flags while they sang, shouted and chanted. Several Japanese flags were burned.

About 10,000 Chinese also marched on a Japanese department store in the city of Shenzhen, also in the Guangdong province.

CNN's Tara Duffy in Beijing said on Monday that Chinese authorities have been urging protesters to remain calm but has been allowing them to go ahead.

Still, authorities have controlled media reporting of the protests.

"Chinese media is not reporting the protests in any major way...CNN's reporting of the protests on Sunday was blocked out," she said.

Japanese press attache Ide Keiji (井出敬二) told reporters Sunday that Japan's envoy Koreshige Anami talked by phone with China's Deputy Foreign Minister and called Saturday's protest, in which rocks and bottles were thrown at the Japanese embassy, "gravely regrettable."

Ambassador Anami also asked the Chinese government to take all necessary measures to protect Japanese citizens in China, Ide said.

The Japanese spokesman said the Chinese Deputy Foreign Minister expressed regret on behalf of his government for the Saturday protest and said the Chinese government could not allow it to happen again.

The protests are targeted at Japan's bid to become a permanent U.N. Security Council member and have been made more emotional by Chinese objections to how Japanese school textbooks recount Japan's 20th century military campaigns.

The protesters in Beijing Saturday chanted anti-Japanese slogans, sang patriotic songs, waved Chinese flags and carried banners critical of Japan.

Some protesters threw rocks and plastic water bottles toward the embassy gate. The messages included a call for China to boycott Japanese products.

Hundreds of military police in riot gear lined up outside the embassy, while hundreds more police blocked nearby streets to keep the number of protesters down. Police moved in to end the protest after about an hour.

It was the biggest protest in the Chinese capital since 1999 when angry crowds demonstrated outside the U.S. Embassy after three Chinese were killed when the Chinese Embassy in Belgrade, in what was then the Yugoslav capital, was accidentally bombed.

That came during the NATO air war against the Serb-led forces in the Serbian province of Kosovo, where Serbs and ethnic Albanians had been fighting.