BEIJING (PTI): China's indigenously-built second aircraft carrier Shandong will undergo its first maintenance and comprehensive examination amidst speculation over the delay in attaining its operational readiness despite two years after entering service.

The Shandong, China's second aircraft carrier and the first developed domestically, reportedly started its first scheduled maintenance and refurbishment that is expected to enhance the flattop's usability, state-run Global Times reported on Monday.

A comprehensive examination to the carrier could be carried out and upgrades and overhaul could be made to those parts that encountered problems or can be optimised based on the experiences gained over the past two years, the daily quoted an expert as saying.

The report of Shandong to undergo overhaul followed reports of delay of the launch of China's third aircraft carrier due to the current surge of COVID-19 in Shanghai where it was being built.

The People's Liberation Army Navy (PLAN) was widely expected to launch the aircraft carrier around its 73rd anniversary on April 23.

But the plan faces delay as the rampant pandemic in Shanghai has delayed the transport of some key components, the Hong Kong-based South China Morning Post newspaper recently reported.

Construction of the Type 003 aircraft carrier has been underway at the Jiangnan Shipyard on Shanghai's Changxing Island since 2017 and was expected to be ready for launch early this year.

China's first aircraft carrier, the Liaoning -- a refit of the Soviet-era ship which was commissioned in 2012, is so far the only Chinese aircraft carrier with initial operational capability or the basic level of combat readiness.

China launched its first indigenously-built aircraft carrier Shandong in 2019.

However, no official reason has been given as to why Shandong has not reached the combat-readiness stage, the Post report said, sparking speculation that the first domestically-built aircraft carrier faced operational problems.

The Global Times report said that the overhaul procedures could involve the painting of new non-skid coating as well as repairs and upgrades for some subsystems, and the carrier would come back stronger than ever in a few months.

Last month, Shandong sailed through the Taiwan Straits from south to north without aircraft on its flight but later reports said it was on way from its homeport Sanya to Dalian shipyard for maintenance.

According to official media reports, China plans to build at least four aircraft carrier strike groups by 2030 to become the world's second-biggest modern blue-water navy after the US.

On Saturday, the PLA Navy celebrated its 73rd anniversary by announcing the commissioning of half a dozen powerful warships and two types of advanced vessel-based helicopters.

An official video introducing China's aircraft carrier programme released on Friday also gave a very obvious hint that the country's third aircraft carrier will be officially revealed soon, a previous report by the Global Times said.

On the PLA Navy's birthday, at least six new surface vessels were commissioned, namely a Type 075 amphibious assault ship, three Type 055 large destroyers and two Type 052D destroyers, the report said.

Early this year, China hiked its annual defence budget by 7.1 per cent to USD 230 billion from last year's USD 209 billion.

China is rapidly modernising its Navy, including the building of new aircraft carriers.

Chinese President Xi Jinping, who heads the military besides the ruling Communist Party of China, has carried out extensive reforms of the military including downsizing of the Army and enhancing the role of the Navy and the Air Force as Beijing has set its sights on global expansion with military bases in Djibouti, the Horn of Africa.

China has also taken over Sri Lanka's Hambantota port for a 99-year lease and expanded and modernised Pakistan's Gwadar port in the Arabian Sea.