The restrictions imposed on Singapore Air Force planes by Malaysia on Thursday are the latest in a long line of disagreements between the island state and its neighbour to the north.

But many analysts see this as less an issue of airspace and more a matter of diplomatic pique in Kuala Lumpur at the recent publication of Singapore Senior Minister Lee Kuan Yew's memoirs, which contained passages critical of Malaysia.

Disputes between Singapore and Malaysia are by no means a new phenomenon.

After initial attempts at integration within a post-colonial federation of Malaysia in the early 1960s, political and ethnic tensions forced Singapore to secede in 1965.

Relative political stability and Prime Minister Lee Kuan Yew's aggressive policy of economic growth enabled the island state to punch above its weight in South East Asia.

On the back of Singapore's rapid development, Prime Minister Lee acquired a reputation as a political heavyweight, but he has been accused of taking a condescending attitude towards Malaysia.

Intellectual leadership

Although Mr Lee stepped down as Prime Minister of Singapore in 1990, he has continued to exert significant influence and remains an influential figure across the region.

Lee Kuan Yew: Influential elder-statesman

Yet ironically, the two leaders have seen eye-to-eye on the controversial issue of 'Asian values'. Both share the belief that Asian societies differ fundamentally from Western societies in their structure, priorities and morality.

However, they have crossed swords more frequently than they have joined hands.

Last year, Dr Mahathir made fun of a Singaporean initiative to prevent vandalism of public property by accusing Singaporeans of being the sort of people who "urinate in lifts".

For his part, Mr Lee created indignation in Malaysia for describing the Malaysian town of Johor Bahru as "notorious for shootings, muggings and car-jackings."

Dr Mahathir: Under fire from political opponents at home

The memoirs, published earlier this week, contain several passages critical of Malaysia, which once again has seen Mr Lee's remarks as deliberate provocation.

With the Malaysian economy still reeling, and Dr Mahathir coming under unprecedented criticism from his sacked deputy, Anwar Ibrahim, Mr Lee's comments may seem to have given the embattled Dr Mahathir a rallying point for Malaysian opinion.

Uncertain climate

But Mr Lee may be more concerned about driving home one of the main points of his book: that Singapore is vulnerable, and that the younger generation of Singaporeans should not take anything for granted in the current uncertain climate of South East Asia.

Malaysia's reaction will only serve to confirm that point.

This latest friction could also have broader implications. Lacking security institutions like Nato, further political tensions between Kuala Lumpur and Singapore could affect security in the East Asian region.

ASEAN's natural leader, Indonesia, is paralysed by its own internal problems, and so Singapore's relations with Malaysia have become increasingly important to provide some kind of firm security foundation for a weakened ASEAN.

This dispute could further weaken the idea of ASEAN cooperation. And it could dilute the credibility of what is already a rather toothless political body.

But if Singapore-Malaysian relations have been rocky, they have usually managed to come back to some sort of even keel.