Incidents of armed robbery reported in the Singapore Strait have hit a five-year high.

There were 16 incidents from January to June this year, compared with eight in the same period last year.

Overall, the increase in piracy and armed robbery was notable throughout Asian waters in the first half of the year, with 51 reported incidents against 28 for the same period last year.

The half-yearly statistics were released by the Regional Cooperation Agreement on Combating Piracy and Armed Robbery against Ships in Asia (ReCAAP) Information Sharing Centre on Thursday.

ReCAAP's executive director Masafumi Kuroki told reporters in a virtual briefing that the centre was concerned with the nearly twofold increase in the number of incidents in Asia, even though most were at a "low severity level".

"Small crimes, if not addressed, can embolden criminals to commit more serious acts," he said.

Most of the incidents in the Singapore Strait this year occurred in the hours of darkness and involved bulk carriers, although tankers and tug boats were also targeted. Items stolen included engine spares, scrap metal and steel construction material on barges.

The number of incidents in the Malacca and Singapore straits has climbed steadily from one in the first half of 2016 to two in the following year and five in 2018.

Asked about the increase in the number of incidents, Mr Kuroki said the reasons were not clear, but there was a need for ships to enhance their vigilance and for law enforcement to strengthen surveillance and patrol.

One bright spot was the arrest of three perpetrators on a bulk carrier by the Indonesian Navy on March 16.

The carrier was about 6.8 nautical miles east of Pulau Karimun Kecil, in Indonesia, at about 5am, when the perpetrators were sighted in the engine room and were detained by the crew. The crew members were not injured and nothing was stolen.

Mr Kuroki said he hoped for more of such arrests in the Singapore Strait, which would be an important factor in reducing the number of incidents.

He also said arrests made by the Indonesian authorities in 2014 and 2015 had drastically reduced the number of incidents in 2016.

He noted that while the spike in incidents in Asia has coincided with the Covid-19 pandemic, it was difficult to find any causal relation between the two.

He said: "We are not a research institute. We are not doing any study, or have any data to assess the relationship between Covid-19 and incidents in Asia."

The number of incidents of piracy and armed robbery reported in Asian waters reached its lowest in more than a decade in 2018, with 76 cases. This increased slightly to 82 last year.

Reports of incidents are collated from designated government agencies of ReCAAP's 20 member states, which include Singapore, India, the Philippines, Japan, Australia and the United States.

The Maritime and Port Authority is Singapore's designated agency.

Recent efforts by Singapore to tackle piracy include the restructuring of the navy's Maritime Security Task Force.

In January, the Republic of Singapore Navy also hosted a Malacca Strait Patrol Joint Coordinating Committee Meeting with representatives from Indonesia, Malaysia and Thailand.