East Asia is bracing for an era of tension and confrontation after Japan's general elections returned a hawkish conservative to power.

The Liberal Democratic party's resounding victory on Sunday threatens to further impair relations with China if the new prime minister, Shinzo Abe, makes good on promises to take a tough stance in a territorial row.

Yesterday's result marked a dramatic comeback for the LDP, three years after it was ousted by the left-of-centre Democratic Party of Japan (DPJ), ending its near monopoly on power for five decades.

Abe, who is expected to be installed as Japan's seventh prime minister in six years on Boxing day, has vowed to strengthen Japan's military in the face of Beijing's more aggressive posture in the East China Sea and North Korea's ballistic missile and nuclear weapons programmes.

A furious reaction is expected from Beijing if the LDP goes ahead with campaign pledges to develop fisheries and build on the Senkakus, a group of islands administered by Japan but also claimed by China, which calls them the Diaoyu.

China's Xinhua news agency warned Japan to resist the shift to the right that has characterised the election, held months after Chinese demonstrators attacked Japanese businesses following Japan's purchase of the islands from their private owners.

"An economically weak and politically angry Japan will not only hurt the country, but also hurt the region and the world at large," Xinhua said. "Japan, which brought great harm and devastation to other Asian countries in the second world war, will raise further suspicions among its neighbours if the current political trend of turning right is not stopped in time."

Some analysts believe Abe, who resigned as prime minister in 2007 after only a year in office, will adopt a more conciliatory approach towards China – Japan's biggest trading partner – once the realities of political office kick in, citing his fence-mending visit to Beijing early during his previous term as prime minister.

"For all his nationalist credentials, I suspect Abe will be more pragmatic," said John Swenson-Wright, senior consulting fellow for Asia at Chatham House. "If he's in this for the long game and wants to last longer as prime minister than he did the first time, he certainly has the motivation to be more pragmatic."

Koichi Nakano, a political science professor at Sophia University in Tokyo, predicted Abe would come under pressure from his own party to implement his hawkish agenda. "During his campaign to lead the LDP, he said he regretted moderating his stance on China the first time he was prime minister," Nakano said. "This is his last chance, so will he want to go down as someone who moderates his views when in office, or as a conviction politician? My feeling is that he'll go for the latter.

"The right wing of the LDP installed him as party leader, and I don't think he has the authority or the personality to keep a grip on them. They chose him because they know he's easy to manipulate."

Speaking on TV after his victory, Abe, 58, signalled that he would make the economy his priority. "First and foremost we have to bring about an economic recovery and pull Japan out of deflation," he said. The economy had been in dire straits for three years and was his top priority.

"We must strengthen our alliance with the US and also improve relations with China, with a strong determination that there is no change in the fact that the Senkaku Islands are our territory."

Exit polls indicated the LDP was on course to win about 300 seats, and its traditional ally, New Komeito, about 30 seats. Combined, that would give them the "supermajority" they need in the 480-seat lower house to pass legislation through both houses of parliament unchallenged.

The incumbent prime minister, Yoshihiko Noda, whose DPJ is expected to win 65 seats – a fifth of the number it won in 2009 – said he would resign as party leader to take responsibility for its heavy defeat. "I apologise deeply for our failure to achieve results," he said. "This was the voters' verdict on our failure to live up to their expectations during our three years and three months in power."

Abe also supports revisions to the constitution to give Japan's military a more prominent role, and is expected to reverse Noda's decision to abandon nuclear power – a response to last year's triple meltdown at Fukushima Daiichi nuclear power plant – by 2040.

Under Abe, Japan can expect a return to high spending on public works – a clear sign that the conservative old guard has returned.

The election also saw the emergence of a third force in the form of the Japan Restoration party, a far-right group led by the outspoken former governor of Tokyo, Shintaro Ishihara, that was predicted to win between 40 and 61 seats.

At one point, polls suggested that the Restoration party could overtake the DPJ as the country's second-biggest party and act as powerbroker in a hung parliament.

That level of influence now looks unlikely, but LDP officials suggested the new administration could turn to Ishihara for support if it decides to revise the constitution – another measure expected to antagonise China and South Korea.