London open: Assault on 6,000 begins

Blue chips have had a first stab at hitting the magic 6,000 level following gains in the US overnight and are regrouping after falling just one point short.Insurer Old Mutual is among the early winners, followed by Sainsbury's and Kingfisher, but ARM is giving back a little of yesterday's big gains. Miners have also dipped and HSBC is off colour on fears about further monetary tightening measures in China.Oil prices closed above $90 a barrel for the first time since October 2008 yesterday following a bigger than expected decline in US crude supplies last week. That's giving BP and Royal Dutch Shell a lift this morning.Rio Tinto has increased its offer for Riversdale Mining to A$16 a share in cash, securing the backing of management for a deal worth A$3.9bn (£2.5bn). The mining giant admitted earlier this month it had talked to the Sydney-based firm, which has interests in African coal, about a A$15 a share takeover valuing the business at £2.2bn (A$3.5bn).Pharmaceuticals giants AstraZeneca and Abbott have dissolved their collaboration agreement covering the development of Certriad capsules. After the US FDA issued a Complete Response Letter for the Certriad new drug application the two companies decided that the resulting regulatory delay meant development of Certriad is no longer commercially attractive. Outsourcing giant Capita has announced two bolt-on acquisitions. It is buying hotel and meetings bookings firm BSI for £42.5m, and ICT services provider SunGard Public Sector Holdings for £86m.