SYDNEY, Australia--China is harassing Indonesian and Malaysian oil exploration ships, proving its determination to assert sovereignty over the far-flung corners of the South China Sea.

Just last month, China’s Chairman Xi Jinping sought to reassure his Southeast Asian neighbours with a promise he “absolutely will not seek hegemony or even less, bully the small”.

Even as the words left his lips, his coast guard ships were doing the exact opposite.

And their targets were some of China’s most committed supporters in the region.

Kuala Lumpur has summoned the Chinese envoy twice this year to protest “interference” with attempts to survey Malaysian waters for gas and oil.

Beijing had also ordered Jakarta to stop drilling near the Natuna Islands on the grounds it was within “Chinese territory”. It sent a survey ship, accompanied by coast guard and naval vessels, to harass the search.

Washington-based think-tank Asian Maritime Transparency Initiative (AMTI) says exploration vessels operating in Malaysian waters have long been subject to such coercive tactics. But Beijing has this year begun extending the tactic to Indonesian waters.

AMTI analyst Gregory Poling says Beijing has become “increasingly bold” over the past year after completing its armed island fortresses in the Spratly Islands. These are acting as launch pads for its fishing militia, coast guard and navy deep into the southern South China Sea.

Now the US Secretary of State, Antony Blinken, is visiting the region in a bid to unify opposition to China’s “bullying” and discuss a new US-led Indo-Pacific economic agreement.

Nine-dash clash

The South China Sea has become a battleground as China seeks to secure the strategic fishing, trade and energy hub.

Beijing claims 85 per cent of the sea under an arbitrary “nine-dash line” claim first made in the 1940s. An attempt to justify this assertion based on “historic ownership” was rejected by an international court of arbitration.

Beijing ignored the ruling, insisting no court other than Chinese courts have jurisdiction over the sea.

Vietnam, Malaysia, the Philippines and Taiwan have long accused Beijing of using paramilitary fishing militia boats to enforce its claims under a thin veneer of plausible deniability. All have also had efforts to harness oil and gas reserves within their waters aggressively opposed.

But this is the first time Indonesia has faced such Chinese opposition.

Mr Poling says neither Malaysia nor Indonesia had sought to “publicise Chinese bad behaviour in the way that Vietnam and the Philippines do”.

But growing internal unrest at the territorial struggles has seen this change.

“Malaysia has become more vocal in the last two to three years, though it still avoids talking about most cases of Chinese harassment since there is little it can do to stop it,” Mr Poling says.

And Indonesia, despite having become “noticeably less vocal in recent months than it was the last time there was large-scale Chinese harassment”, has released damning details of China’s demands.

Indonesia backed into a corner

Chinese diplomats earlier this year delivered a letter to Jakarta ordering it to halt the drilling of an offshore rig near Natuna Island at the South China Sea’s southernmost extremity.

Indonesian member of parliament Muhammad Farhan, a member of the National Security Committee, says Indonesia refused to comply.

“Our reply was very firm, that we are not going to stop the drilling because it is our sovereign right,” he reportedly said.

The rig was operating within Indonesia’s 370km exclusive economic zone (EEZ), as defined by the 1982 United Nations Convention on the Law of the Sea (UNCLOS). Beijing is a signatory to the treaty.

It was a risky move.

Indonesia is China’s biggest client under the Belt and Road Initiative. Jakarta has sought to be “as silent as possible because, if it was leaked to any media, it would create a diplomatic incident,” says Mr Farhan.

In recent years, Beijing’s fishing militia has regularly intruded on Jakarta’s EEZ. But a new standoff, which began in June, is the first time it has attempted to block commercial drilling operations.

China’s initial protest letter was followed by repeated demands to halt the search within the “Tuna Block” area of the Natuna Sea.

Indonesia, however, refuses to acknowledge such demands as “there is nothing to discuss”.

Beijing sent an armed Coast Guard vessel. Later, the large oceanic research vessel the Haiyang Dizhi 10 was escorted by two Coast Guard cutters into the area.

In September, the US aircraft carrier USS Carl Vinson passed close to the Indonesian drilling operation. China responded by deploying a destroyer and five other warships.

Mr Farhan says China also sent a letter of protest over an August military land exercise between Indonesia and the United States. It’s the first time such a protest has been made despite the event being held regularly since 2009.

Indonesia’s Minister of Maritime and Investment Affairs, Luhut Binsar Pandjaitan, has attempted to play down the standoff, saying “we respect freedom of navigation in the Natuna Sea”.

Malaysia’s conflicted interests

Like Indonesia, Malaysia claims the full EEZ entitlement to the South China Sea as defined by the Law of the Sea. This includes an extended “continental shelf” claim submitted in co-operation with Vietnam in 2009.

Unlike Indonesia, Malaysia also claims part of the Spratly Islands. Kuala Lumpur maintains a permanent presence on five of the 12 features it says are its sovereign territory.

But Beijing’s militia and Coast Guard efforts have primarily been focused on Luconia Shoals off the coast of Malaysia, where several oil and gas explorations efforts are underway.

“They manoeuvre dangerously and intentionally create risks of collision to dissuade civilians from accepting such contracts,” says Mr Poling.

The Lacona Shoals Kasawari field is particularly rich. The Petronas energy company hopes its exploitation will propel it to become the world’s fifth-largest exporter of liquefied natural gas.

But Malaysia’s Foreign Minister, Saifuddin Abdullah, says he expects Chinese vessels to intrude in the waters “for as long as Petronas continues to develop the field”.

Saifuddin, however, says Kuala Lumpur has reached an agreement with Beijing that “peace and stability” must be maintained in the South China Sea.

He described the confrontation as a “small hiccup” in the two nations’ bilateral relations.

“We have been agreeable on the ways (on) how we solved issues. And, as a member of ASEAN, we appreciate the fact that China is also working with us on the conclusion of the Code of Conduct,” Mr Saifuddin said during a recent visit to Chana.

But little progress has been made on the Code since China proposed it in the early 2000s.