* China's 'dangerous' actions could cause contingency -white paper
* North Korea missile technologies advancing -white paper
* Japan eyes beefing up defence posture
Japan faces increasingly serious threats to its security from China and North Korea, a defence ministry report said on Tuesday, as ruling politicians call for the military to beef up its ability to respond to such threats.
The report was likely to prompt a sharp response from Beijing, whose ties with Tokyo are strained by a territorial row and remarks by Prime Minister Shinzo Abe suggesting he wants to cast Japan's wartime history in a less apologetic tone.
"There are various issues and destabilising factors in the security environment surrounding Japan, some of which are becoming increasingly tangible, acute and serious," the annual defence white paper said.
"China has attempted to change the status quo by force based on its own assertion, which is incompatible with the existing order of international law."
China and Japan have been locked in a dispute over rival claims to a group of tiny East China Sea islets.
Patrol ships from both countries routinely shadow each other near the islands, raising concerns that an unintended collision or other incident could lead to a broader clash.
"Some of China's activities involve its intrusion into Japan's territorial waters, its violation of Japan's territorial airspace and even dangerous actions that could cause a contingency, and are extremely regrettable," the paper said.
Defence Minister Itsunori Onodera said in February that a Chinese naval vessel had locked its fire control radar on a Japanese destroyer. Directing such radar at a target can be considered a step away from actual firing.
China denied the warship had locked its radar on the Japanese vessel. But the white paper said Beijing's assertion was "inconsistent with the facts".
Abe returned to power for a rare second term after his ruling bloc won a general election late last year, promising to revive the economy and strengthen Japan's defences. He also wants to revise the post-World War Two pacifist constitution to legitimise the military, although winning support for contentious revisions is likely to take time.
Japan is already bolstering its islands' defence and this year raised its defence budget for the first time in 11 years.
The military is conducting joint drills with the United States, its main security ally, and fortifying defences against missile attacks, while the government is reviewing its mid-term defence policy.
BALANCE OF POWER
Japan plans to draw up a new defence plan by December, and Abe's Liberal Democratic Party (LDP) last month submitted to the government recommendations that included looking into acquiring the capability to attack enemy targets.
Japan has long maintained that it has the right to strike enemy targets when an intention to attack Japan is clear, the threat is imminent and there are no other options.
But any sign that Japan is moving to obtain such capabilities could upset China and South Korea, where resentment against Japan's wartime aggression and colonisation runs deep.
The LDP also recommended that, in order to boost the defence of remote islands, the military should set up an amphibious Marines division equipped with tilt-rotor aircraft like the V-22 Osprey.
"The balance of power will be lost if we don't start considering striking back when attacked," said Osaka University professor Kazuya Sakamoto, who sits on a panel advising Abe on security policies.
"If we don't have weapons that reach an enemy, Japan cannot defend itself. It cannot maintain deterrence."
Such moves, Sakamoto added, should not unnerve China, with its arsenal of nuclear weapons.
Abe, whose LDP is expected to cement its grip on power in this month's upper house election, also wants to revise an interpretation of the constitution that bans using the right of collective self-defence, or aiding an ally under attack.
A panel set up during Abe's first 2006-7 term recommended that the ban be lifted in certain cases, such as intercepting ballistic missiles bound for the United States. A new committee of advisers is expected to reach similar conclusions.
North Korea launched a missile in December, stepping up the threat that the isolated, impoverished state poses to rivals. In February, it conducted a third nuclear test, which moved Pyongyang closer to developing long-range nuclear missiles.
"The launch of a missile ... showed that North Korea has advanced its technologies to extend the range and improve the accuracy of ballistic missiles," the white paper said.
The report added that if North Korea develops ballistic missiles based on technologies tested in December, they could reach the central and western parts of the U.S. mainland.
Japan's defence spending has fallen 5 percent in the past decade even after this year's small gain. China saw its defence budget quadruple during the same period, the white paper said.