Officials from Taiwan and mainland China signed four agreements in Taipei yesterday in the latest show of firming cross-Strait economic ties, AFP reported. Among the agreements, direct cross-Strait cargo flights will be introduced, with up to 60 round trips per month, while direct passenger flights will be tripled to 108 per week. China will also expand the number of cities with air links to Taiwan from the current five to 21. The two sides also agreed to introduce cross-Strait postal services and pledged to hold future discussions on food security. Direct cargo air links would cut shipping costs by 15-30%, said Chiang Pin-kung, head of the Strait Exchange Foundation and a participant in the talks.