Philippine government websites are under heavy attack from hackers, apparently from China, amid a tense territorial dispute between the two countries in the South China Sea, officials said Thursday.

While some Philippine hackers have reportedly launched retaliatory attacks, the government appealed to them for restraint, said Roy Espiritu, spokesman of the government's information technology office.

"We've actually detected several attacks, including attempts at distributed denial of service," he said, in which a hacker infiltrates computers with which to attack a single target, such as a website, forcing it to shut down.

"They (hackers) are probing into different (Philippine) government domains so we can't say how many attacks there are. But it is a lot," Espiritu told AFP.

"The signatures (of the hackers) indicate they are from Chinese networks."

Espiritu conceded this could be a ruse and the attacks may have actually originated from other sources.

But he said all the attacks came after Philippine ships faced off with Chinese patrol vessels in April 8 in the disputed Scarborough Shoal in the South China Sea. Before that, there had been no such attacks.

The Chinese vessels initially prevented the Philippine Navy from arresting alleged Chinese poachers in the area. The stand-off is continuing.

Budget Secretary Florencio Abad said his agency's website had again been defaced on Wednesday, just days after a similar hacking attack.

Earlier, three of President Benigno Aquino's websites and a state university website were also attacked, supposedly by hackers from China.

In at least one case, the hackers left a message asserting China's claim to the South China Sea.

Espiritu said the technology office had implemented its own "firewall procedures" to fend off many of the attacks and was working with law-enforcement agencies to investigate them.

He called for restraint from vengeful local hackers. "We would like to request them to be the bigger man and not escalate the situation."