Equity markets came under pressure and volatility expectations rose after president donald trump announced that he and the first lady had tested positive for coronavirus just weeks ahead of the us presidential election.

European bourses opened lower on friday, with the region-wide stoxx 600 down 0.8 per cent, londons ftse 100 down 0.7 per cent and germanys dax down 1 per cent after the opening bell.

Trading was choppy in us stock index futures several hours before the opening bell on wall street. s&p 500 futures, which are relatively thinly traded in the early european hours, were recently down 1 per cent.

Mr trumps diagnosis just over a month before polling day comes as investors were already bracing themselves for a sharp jolt of market tumult induced by the election. wall streets vix volatility index rose 2 points on friday morning to 28, with futures contracts also pointing to heightened expectations for turbulence in november and december.

Were in a situation where there are more questions than answers, said robert rennie, head of market strategy at westpac. mr rennie said investors were likely to shun riskier assets until there was greater clarity on the outlook for the health of mr trump and others in the white house.

This is happening at the beginning of october and weve still got four weeks to go...certainly the path ahead is one of extreme uncertainty to the start of november and potentially beyond, he added.

Japans yen, which often rises during times of greater uncertainty as domestic investors pull funds back into the domestic market, strengthened 0.5 per cent against the dollar to 105.01.

Us treasuries, considered to be a haven asset, rose modestly in price, pushing yields slightly lower.

Oil prices, which have taken a hit this month on concerns of falling demand, fell further on friday, with brent crude, the international benchmark, down 3.2 per cent to $39.62 a barrel, close to its low of the month.

Some investors suggested it was not yet clear what the broader implications of mr trumps diagnosis were for markets. the market cant really work out yet whether this represents a big risk-off moment, so its too soon to say how this will play, said one tokyo-based trader.

Analysts have other sources of uncertainty to contend with: lawmakers in the us remain at odds over a new fiscal stimulus package. the deadlock is being closely monitored by economists who fear the withdrawal of support would be a blow to the us recovery.

Data released on thursday showed a 2.7 per cent drop in personal income in august as government support measures lapsed. analysts will be closely watching the latest monthly jobs report released later on friday.

In europe, englands largest coronavirus infection survey indicated that the growth rate of infections was beginning to slow. but the government warned that further restrictions could still be imposed, while new rules were announced in spains capital.

The eu urged caution about the progress of brexit talks, which are due to end on friday. brussels is suing the uk over plans to violate last years withdrawal agreement.

In the asia-pacific region, tokyos benchmark topix dropped 1 per cent after earlier rising by nearly the same level, while australias s&p/asx 200 shed 1.4 per cent.