Investors were also digesting weak US jobs data, while crude prices climbed after eight key members of the OPEC+ alliance said they had agreed to again boost oil production.

"A combination of weak US labour market data coupled with rising political uncertainty in Japan dominated global markets as we started the week in Asia," Michael Wan at MUFG said in a note.

Tokyo's Nikkei index gained 1.9 percent, with Japanese exporters benefiting from a slide in the yen's value -- one dollar bought 148.14 yen in morning trade, up from 147.07 yen on Friday.

Japanese bond yields also climbed after Ishiba said Sunday he would step down after less than a year in power, heralding fresh uncertainty for the world's fourth-largest economy.

"I don't think we can say that the resignation of PM Ishiba is a complete surprise as it's been mooted for some time but the timing of the announcement is certainly unexpected," said Michael Brown, senior research strategist at Pepperstone.

"As for the market reaction, this obviously introduces significant downside risks for the (Japanese yen) and for long-end" Japanese government bonds (JGBs), he added.

Last week, the yield on 30-year JGBs hit a record high, following rises in the United States and Europe on the back of concerns about political uncertainty and public finances.

Potential candidates to be leader of Japan's ruling party are "all likely to propose looser fiscal stances than Ishiba, hence further pressuring the long end of the curve, where demand for JGBs had already been waning quite significantly", Brown said.

Hong Kong and Shanghai were 0.3 percent higher in morning trade, with Taipei up 0.5 percent and Seoul also gaining 0.3 percent.

Singapore rose 0.1 percent and Wellington was up 0.1 percent, but Sydney fell 0.3 percent.

Last week's US jobs data has cemented expectations of a Federal Reserve interest rate cut later this month.

In Asia, "rising expectations of Fed rate cuts and with that lower US yields should be a welcome development to some extent providing some breathing space and policy room for Asian central banks", said Wan of MUFG.

"Nonetheless, the key risk for Asian currencies would also lie in a sharp US slowdown and hard-landing recession through sharply slower exports to the US, which we stress is not our base case."

- Key figures at around 0200 GMT -

Tokyo - Nikkei 225: UP 1.9 percent at 43,816.02

Hong Kong - Hang Seng Index: UP 0.3 percent at 25,499.10

Shanghai - Composite: UP 0.3 percent at 3,825.83

Euro/dollar: DOWN at $1.1711 from $1.1722 on Friday

Pound/dollar: DOWN at $1.3501 from $1.3508

Dollar/yen: UP at 148.14 yen from 147.07 yen

Euro/pound: DOWN at 86.75 pence from 86.77 pence

West Texas Intermediate: UP 1.3 percent at $62.66 per barrel

Brent North Sea Crude: UP 1.3 percent at $66.32 per barrel

New York - Dow: DOWN 0.5 percent at 45,400.86 (close)

London - FTSE 100: DOWN 0.1 percent at 9,208.21 (close)