Jan 21 (Reuters) - Property and casualty insurer Travelers Cos Inc reported a jump in quarterly profit on Thursday, helped by an increase in returns from investments and lower catastrophe claims. The company reported a core income of $1.26 billion, or $4.91 per share, in the fourth quarter ended Dec. 31, compared with $867 million, or $3.32 per share, a year earlier. Analysts had expected a profit of $3.18 per share on average, according to Refinitiv data. It was not immediately clear whether the estimates were comparable. New York-based Travelers, often seen as a bellwether for the insurance sector as it typically reports before its industry peers, said net written premiums rose 3% to $7.27 billion for the reported quarter. The insurer’s strong quarter caps off a year of the COVID-19 pandemic, which has had a far less impact on property casualty insurers than many investors expected, mainly because of pandemic-related exclusions in their contracts. Travelers’ underwriting gains rose to $955 million from $513 million a year earlier, while pre-tax net investment income rose 10% to $677 million, helped by gains in its non-fixed income investment portfolio. The company reported a combined ratio of 86.7%, compared with 92.4% a year earlier. A ratio below 100% means the insurer earned more in premiums than it paid out in claims.