MANILA (Reuters) - China has scaled down its presence at a disputed South China Sea shoal but has not interfered with Filipino fishermen, the Philippine president’s security adviser said on Sunday, after the administration had said China had withdrawn completely.

A fisherman repairs his boat overlooking fishing boats that fish in the disputed Scarborough Shoal in the South China Sea, at Masinloc, Zambales, in the Philippines April 22, 2015. REUTERS/Erik De Castro/File Photo

Hermogenes Esperon said Chinese ships were still present but had not blocked Filipino boats at the Scarborough shoal, a rocky outcrop central to an international arbitration case, since President Rodrigo Duterte’s visit to Beijing two weeks ago.

The situation at sea remains unclear, however, as do the circumstances behind an apparent softening of China’s position regarding an area significant not only for fishing, but for the broader balance of power in the South China Sea.

China had repelled fishermen since seizing the Scarborough Shoal in 2012, but Filipino boats returned from the area at the weekend with tonnes of fish, broadcaster GMA reported, showing images of smiling crew and a large catch.

Philippine Defence Secretary Delfin Lorenzana had on Friday declared Chinese vessels were no longer there and fishing could resume. Duterte’s spokesman also made similar comments.

However, Esperon said military monitoring of the situation showed a reduced Chinese presence, but not a total withdrawal.

“From Oct. 17 to 27, there had been only two Chinese ships,” Esperon said in a text message. “There are no written agreements or rules but Filipino fishermen who went there lately attest that they were not driven away.”

He said in the past, on an average day, there had been about five Chinese navy and four coastguard ships.

China’s blockade of what is a prime fishing spot prompted the previous Philippine government to take on China by filing a case in 2013 at the Permanent Court of Arbitration in The Hague, infuriating Beijing.

The tribunal’s July ruling, which China refuses to acknowledge, declared the shoal a traditional fishing ground that Chinese, Philippine and Vietnamese could all exploit. It also invalidated China’s claims to most of the South China Sea.

A frosty Philippine-China relationship changed dramatically after Duterte took office four months ago and started praising China while denouncing the United States in a sudden reversal of his predecessor’s foreign policy.

China’s Foreign Ministry was asked by media on Friday about the situation at the shoal but gave a non-committal answer.

Returning fishermen said two or three Chinese coastguard ships circled the shoal but had not harassed them.

Esperon said a Chinese survey ship was seen near Scarborough on Oct. 19 and a navy frigate the following day, but when Duterte returned home from Beijing, they left the area.

He said there had been no update on the situation since Friday, but a defense source told Reuters a surveillance plane had on Saturday seen four Chinese ships at the shoal.

A senior coastguard official, who declined to be named because he was unauthorized to speak to the media, said a Chinese withdrawal appeared unlikely.

“China will not abandon this area but if it will no longer harass local fishermen, that’s a positive development,” the official said.