SEN. Risa Hontiveros slammed China on Tuesday for propagating "lies" that the Atin Ito civilian humanitarian mission to the West Philippine Sea (WPS) was organized by the Philippine and United States governments.

"China, keep your hands off our vessels and people," the senator said in a statement amid reports that China sent vessels to Bajo de Masinloc (Scarborough Shoal) to block the civilian convoy.

"This group of ordinary and private citizens simply wants to deliver goods to fellow Filipinos whom China has long deprived of food and livelihood," Hontiveros said.

She added, "Not one of the Atin Ito participants should be harassed or intimidated. Not one of our compatriots should fear for their safety."

The China Coast Guard (CCG) played down reports that it dispatched a huge blockading force to Bajo de Masinloc, however.

In a statement, the CCG said they are conducting regular lifesaving training to cement its presence in the contested area. Both the Philippines and China claim Bajo de Masinloc, which the Chinese call Huangyan Island, as their own.

According to the CCG, it has "normalized" the exercises to ensure the safety of Chinese fishing boats in the area.

The announcement of the routine training comes as a civilian-led mission from the Philippines was scheduled to arrive in the area on May 14 to assert Philippine rights in the waters.

"Many Chinese fishing boats are operating in the waters off Huangyan Island, and China Coast Guard regularly conducts lifesaving training at sea to ensure the safety of people on board the ships," the CCG said.

It is the first time the CCG has declared it has normalized a drill near the shoal.

On May 13, retired US Air Force Col. Ray Powell, director of SeaLight, a maritime transparency project that monitors and reports activities in the South China Sea, said they have monitored that China was sending the biggest blockading force ever to Bajo in anticipation of the arrival of the Atin Ito civilian convoy.

"This will be by far the largest blockade I'll have ever tracked at Scarborough. China seems determined to aggressively enforce its claim over the shoal," Powell said.

Atin Ito is a civilian-led supply mission to the Philippine maritime claims in the South China Sea, especially Bajo de Masinloc, which its co-convenor Rafaela David described as a "legitimate exercise of Filipino citizens' right to movement within our own territory."

Bajo de Masinloc is a rich fishing ground located roughly 120 nautical miles west of Luzon and about 590 nautical miles east of China's Hainan Island.

China took control of the shoal in 2012 after a tense stand-off, prompting Manila to launch an international arbitration case over their maritime disputes.

Beijing rejected the 2016 ruling by the Permanent Court of Arbitration in The Hague, which said China's claims to most of the South China Sea had no legal basis.

China's sweeping claims to the resource-rich waterway are also contested by Vietnam, Malaysia and Brunei.

The drill comes amid increasing confrontations between China and the Philippines over the area.

"It is outrageous how China is reportedly sending a huge force to block this civilian mission," Hontiveros said. China acts as if it owns the entire sea, she added.

The Atin Ito civilian mission has every right to set sail for Bajo de Masinloc, Hontiveros said.

"This is our territory. These are our waters. This is ours and only ours," she said.

David, Akbayan Party president and Atin Ito co-convenor, said the civilian supply mission to the WPS was a legitimate exercise of Filipino citizens' right to movement within our own territory.

"Our mission is peaceful, based on international law and aimed at asserting our sovereign rights," she said.

"China's actions are failing to intimidate Filipinos. Instead, they are only uniting us and inspiring us to go further in defending our rights. Atin Ito shall press forward with our peaceful voyage undeterred by any intimidation," David said.

"We will sail with determination, not provocation, to civilianize the region and safeguard our territorial integrity," she added.