Security personnel outnumbered the crowds of Chinese protesting against Japan outside its embassy on Sunday, a day after demonstrations over islands that both nations claim spread across China and turned violent. Japan's leader said the dispute was affecting the safety of Japanese citizens in China.

Rows of paramilitary police lined the perimeter of the embassy in Beijing as police let protesters in groups of up to 100 walk past the building. Many protesters threw items such as water bottles, bananas, tomatoes and eggs at the embassy and chanted slogans asserting that the disputed East China Sea islands, which are controlled by Japan, are Chinese. Dozens carried portraits of Chinese revolutionary leader Mao Zedong, and one man draped the Japanese flag over his dog.

Anti-riot police stood on nearby streets, and around 20 of their vehicles were parked behind the embassy.

In Shanghai, hundreds of protesters across from the main gate of the Japanese Consulate chanted and waved banners. About 50 paramilitary police officers wearing helmets and carrying shields stood outside. Police cordoned off the street and were allowing people to protest in groups of 50 for about 5-10 minutes before escorting them away.

Anti-Japanese sentiment, never far from the surface in China, has been building for weeks, touched off by moves by Tokyo and fanned by a feverish campaign in Chinese state media. Passions grew more heated this past week after the Japanese government purchased the contested East China Sea islands -- called Diaoyu in China and Senkaku in Japan -- from their private Japanese owners.

On Saturday, protesters turned out in more than two dozen cities across China. Thousands gathered in Beijing in front of the embassy, where people burned Japanese flags and clashed with Chinese paramilitary police before order was restored.

Hundreds tried to storm a metal barricade backed by riot police armed with shields, helmets and batons. Many threw rocks, bottles, eggs and traffic cones at the embassy.

The embassy said protesters around the country had set fire to Japanese factories, sabotaged assembly lines, looted department stores and illegally entered Japanese businesses.

In a statement, it asked the Chinese government to ensure the safety of Japanese citizens and businesses in China.

"Unfortunately, this is an issue that is impacting the safety of our citizens and causing damage to the property of Japanese businesses," Japanese Prime Minister Yoshihiko Noda told NHK, Japan's public broadcaster, on Sunday. He said Japan protested the violence, and called on both sides to share information and maintain close communications.

In a sign that the Chinese government is concerned about social disorder spreading, users of China's popular Twitter-like Sina Weibo site couldn't search for the term "anti-Japan protests" on Sunday morning, and many of the previous day's photos had been taken down. The site is regularly censored.

Some postings, however, said there were protests planned Sunday in cities including southern powerhouse Guangzhou and central Xi'an, home of the terracotta warriors, the famed life-size clay statues.

Protesters in southern Shenzhen city demonstrated along a busy commercial street while police looked on.

"Some people are holding banners and portraits of Mao Zedong and chanting slogans to express their patriotism," a woman surnamed Li said by phone. "It's a peaceful protest."

Some online users said they didn't dare drive around in their Japanese brand cars during the weekend.

Japan's ambassador to China died Sunday. Shinichi Nishimiya had fallen ill in Tokyo and had been hospitalized since Thursday, just two days after being named to replace outgoing Ambassador Uichiro Niwa. Japan's Foreign Ministry said it was awaiting a statement from Nishimiya's doctor before releasing more details.