KUALA LUMPUR/HANOI/CANBERRA, March 9 -- More aircraft and ships joined the multinational search operations for a Beijing-bound Malaysian jetliner Sunday, one day after it lost contact with air traffic control.

The priority now is to search and locate the missing Malaysia Airlines flight MH370, Azharuddin Abdul Rahman, director general of Malaysian Department of Civil Aviation, told a press conference in Kuala Lumpur.

A total of 34 aircraft and 40 ships are now searching as the search area has been extended from the South China Sea to the Strait of Malacca, he said.

Regarding the earlier discovery of an oil slick strip off the southern Vietnamese coast, Rahman said chemical test has been done on the oil slicks to confirm whether it came from the missing Boeing 777-200.

He said an investigation has been under way into a possible terror link after authorities found that at least two passengers had boarded the plane using stolen passports. But he declined to give more details.

During phone talks with Malaysian Prime Minister Najib Razak, Australian Prime Minister Tony Abbott said his country will send two P-3C Orion maritime surveillance aircraft to assist in the search for the missing plane.

Abbott said the first P-3C would depart for the search area Sunday evening from Darwin, northern Australia, adding that the second one was to be dispatched as soon as possible.

The P-3C Orion is a long-range maritime surveillance aircraft ideally suited to this task, he said.

In Jakarta, a senior Indonesian navy officer said his country has sent five navy vessels and a maritime surveillance plane to join the search efforts.

"I had been told that our vessels have crossed the northern Malacca Strait boundary lines sometime between 10 and 11 a.m. this morning," said Untung Suropati, a spokesperson for the Indonesian Navy.

He added that the vessels would focus their efforts in Malacca Strait and the northern Malaysian state of Penang.

Also on Sunday, Vietnamese officials said Vietnam has made all-out efforts in close coordination with Malaysia and Singapore to search for the missing plane.

Lt. Gen. Vo Van Tuan, deputy chief of general staff of the armed forces, told reporters that upon receiving relevant information, the Defense Ministry has sent 17 aircraft, 35 ships and a diving team to an area where suspicious oil slicks were found.

Earlier in the day, Vietnamese search and rescue helicopters found oil slicks stretching 80 meters in waters 150 km off the coast of Vietnam's southernmost Ca Mau province.

Pham Quy Tieu, deputy minister of transportation, said Vietnam is ready to coordinate with search and rescue teams from other countries in the area to work out an optimal plan to locate the missing plane.

Meanwhile, the Singaporean Defense Ministry said it has dispatched two more C-130 aircraft, a Formidable-class frigate, a submarine and a missile corvette to joint the search operation.

Chinese President Xi Jinping has ordered all-out efforts for search and rescue.

Two more warships sent by the Chinese navy are en route to the suspected site of the missing plane.

Destroyer Haikou and amphibious landing ship Kunlunshan set off at about 4 p.m. Sunday from two southern ports with a 50-strong marine corps as well as assault boats and rubber dinghies aboard, according to a statement released late Sunday by the Chinese navy.

Meanwhile, two warships dispatched by the navy early Sunday, Mianyang and Jinggangshan, are expected to reach the waters on Monday and Tuesday respectively, officials said.

With medical equipment and materials on board, two helicopters with the Nanhai Fleet joined Jinggangshan on its way for the search.

The Boeing operated by Malaysia Airlines left Kuala Lumpur for Beijing at 00:41 a.m. Saturday, and lost contact at around 1:30 a.m.

The aircraft was carrying 12 crew members and 227 passengers. There has been no confirmed information about the fate of the plane yet.